On the topic of newer mapping/modding standards...

[Sean]

Going by what has been written already, more eyes and players on the project mean more chances people will contribute to something they care about and enjoy.

But there's no one around to actually get more eyes and players and despite all that's been written here (and not just in this thread) nothing's actually happened yet because nobody's invested the actual effort.

People apparently didn't have a problem using their funds for all the necessary services that run Zandronum 12-15 years ago when the average player count was 3-4 times more than it is today. You may not fall under the same category as them, but don't think for a second that there aren't other people with disposable income that would help run things by paying the bills. In all my years of playing, I have seen people come and go all the time who ran servers and port services; there will always be someone willing to step up.

I have invested thousands of my great British pounds in Zandronum, and continue to do so, providing the wiki, Windows CI runner, my own game servers, previously IRC, etc. Not including the free time I spend either. So yes I may fall under the same category as them.

Why would they? There's no exposure that makes Zandro stand out in a sea of OSS and hobbyist game engines. If I were a game dev, how would I know that Zandro exists? Why would I use it over GZDoom? I go onto the Zan website, and I see nothing that tells me why I should use it for my game; I'm instead met with a dusty ass old site from 10 years ago that hasn't updated its presentation to be aligned with modern standards. If I'm trying to develop a game, why would I suddenly stop my own game development to go clean up a game engine’s license problem just so I can begin to even use said engine, when there are other engines ready to go? That is both a stupid scenario and a stupid expectation. There is no chicken vs egg dilemma going on here. You either have something to show and put it out there to be used or you don't.

Have I stumbled into some alternate reality? Zandronum is a Doom source port and always has been. It's not a general-purpose commercial game engine as this thread has suddenly decided it is, and therefore it doesn't function or get marketed as such because we were never developing it under that pretense! If you'd like it to be, that's one thing - but it's not that, and it never has been! That's why.

But also,

Sgt. Mark IV, the creator of Brutal Doom, is literally building his own indie shooter and has publicly said he wanted to ship it with Zandronum pre-packaged, but legally can’t. He spells it out here. This is someone with the clout, the audience, and the will to support the engine and even he has to walk away.

There's apparently someone! But their "will to support the engine" stopped dead at actually having to support the engine. Oh well.

[Catastrophe]

Sean, I don’t think anyone here is trying to dismiss your contributions or imply you're not invested. You've clearly put a lot of time, money, and effort into Zandronum, and that deserves respect. But right now, you're coming off like someone trying to protect what already exists, while ignoring what could exist and that’s exactly what’s keeping this project stuck. No one here is saying, “fix the license so we can cash in on your work.” What we’re saying is: fix the license so people can actually build on this project without hitting a wall. That’s it. It’s not about forcing anyone to help commercial devs. It’s about getting out of the way so new things can happen.

You keep asking why devs haven’t come forward. I’ll answer plainly: because there’s nothing inviting them in. No modern docs, no discoverability, no presentation, and most importantly no legal green light to even ship a standalone game. And the few people who do try, like Sgt. Mark, hit legal roadblocks and walk away. That's not on them. That's on the engine failing to support ambition.

You also said Zandronum was never intended to be a general-purpose engine. Sure. But maybe that’s the problem. If the only long-term goal is to keep it as a multiplayer Doom wrapper, then yeah, the best we can hope for is keeping 50 players online. But if we want to reach anyone outside the small Doom pond, the engine needs to evolve. That means modern systems, modern expectations, and yes, a modern license. Ru5tK1ng is right: more players = more eyes = more potential contributors. That’s not theory. That’s how open source survives. And even if 99% of them don’t become devs, some will. The idea that exposure is somehow dangerous, or that popularity creates more burden than benefit, is backwards. That’s like saying it’s bad to promote your band because now people expect you to play shows.

You also compared this to people profiting off your work without giving back. But here's the thing they already could. The current license technically allows commercial use, provided you follow the GPL. The real reason no one’s doing it isn’t because of the philosophy, it’s because the codebase contains legacy, GPL-incompatible parts that make any serious distribution legally risky. Things like FMOD, Raven code, or unclear third-party bits are what stop people from touching it, not the GPL itself. Cleaning that up doesn’t invite exploitation; it removes the ambiguity so people can actually use the engine for something new without wondering if they’re one DMCA away from having their project pulled.

Nobody’s saying Zandronum needs to become Unity overnight. But if we treat it like it never could be more than a Doom mod launcher, then yeah it’s going to eventually die out on a whimper. People like you have kept it alive this long, and that’s commendable. But keeping something alive isn’t the same as helping it grow. You don’t have to carry the burden of what comes next. But please, stop standing in the way of those willing to try.

[Ru5tK1ng]

Going by what has been written already, more eyes and players on the project mean more chances people will contribute to something they care about and enjoy.

But there's no one around to actually get more eyes and players and despite all that's been written here (and not just in this thread) nothing's actually happened yet because nobody's invested the actual effort.

That's partly due to leadership wouldn't you say? Even though historically there were a lot of useless staff members that just played ircCop, there were plenty others who ran things for the community. I'm not saying that YOU specifically have that responsibility, but it should fall on others who are on the staff. If they can't do it, then they should either step up or step down and let someone else take on the responsibility.

People apparently didn't have a problem using their funds for all the necessary services that run Zandronum 12-15 years ago when the average player count was 3-4 times more than it is today. You may not fall under the same category as them, but don't think for a second that there aren't other people with disposable income that would help run things by paying the bills. In all my years of playing, I have seen people come and go all the time who ran servers and port services; there will always be someone willing to step up.

I have invested thousands of my great British pounds in Zandronum, and continue to do so, providing the wiki, Windows CI runner, my own game servers, previously IRC, etc. Not including the free time I spend either. So yes I may fall under the same category as them.

If that's the case then your previous point makes no sense unless you truly think you're part of a rare breed of people who can cover Zandronum's expense. The community is grateful for your the expenditure of your great british pound, but there are definitely others who can do the same.

Why would they? There's no exposure that makes Zandro stand out in a sea of OSS and hobbyist game engines. If I were a game dev, how would I know that Zandro exists? Why would I use it over GZDoom? I go onto the Zan website, and I see nothing that tells me why I should use it for my game; I'm instead met with a dusty ass old site from 10 years ago that hasn't updated its presentation to be aligned with modern standards. If I'm trying to develop a game, why would I suddenly stop my own game development to go clean up a game engine’s license problem just so I can begin to even use said engine, when there are other engines ready to go? That is both a stupid scenario and a stupid expectation. There is no chicken vs egg dilemma going on here. You either have something to show and put it out there to be used or you don't.

Have I stumbled into some alternate reality? Zandronum is a Doom source port and always has been. It's not a general-purpose commercial game engine as this thread has suddenly decided it is, and therefore it doesn't function or get marketed as such because we were never developing it under that pretense! If you'd like it to be, that's one thing - but it's not that, and it never has been! That's why.

I don't think anyone here has said that Zan is a game engine, rather, it has potential to appeal to certain indie devs. Also, if that was your point from the beginning then you should have just said that instead of purposely being facetious.

But also,

Sgt. Mark IV, the creator of Brutal Doom, is literally building his own indie shooter and has publicly said he wanted to ship it with Zandronum pre-packaged, but legally can’t. He spells it out here. This is someone with the clout, the audience, and the will to support the engine and even he has to walk away.

There's apparently someone! But their "will to support the engine" stopped dead at actually having to support the engine. Oh well.

You might think it's a clever 'gotcha!', but you're just proving the point I made in my previous post. Good job I guess?

[Ivan]

While the current discussion itself has moved a bit from the intention of the original post, it's still very much relevant and resonates a lot with me. As someone who does care about Zandronum, it simply wouldn't sit well with me if I didn't chime in.

I think everyone here to some degree wants this port to get more players. I don't think anyone really wants this port to truly die. Activity afterall brings all sorts of benefits. More players mean more exposure to media, which in turn brings more players. Some of those players may want to help Zandronum develop further with their programming skills, open source and all. Which brings me to my first point: Please, move the repo to Github already. The years of stagnation and lack of anyone showing up to do anything for this port can easily be pointed at this being a strong factor. Most everyone who does any kind of serious Doom engine/modding development is on Github. It's easy to navigate, easy to use. Why don't we use it as well? I don't mean to sound disrespectful, but from what I heard this is due to Torr Samaho's preferences. I don't agree with this, and it's been going on for years only for him to show up for a couple hours a week to give the OK on what commits can go in. Why are we doing this still? Why don't we let more developers in easier through a widely accessible repository system? I have nothing against Torr Samaho on a personal level but some of the decisions that are still going on today are simply creating stagnation and impeding progress. I sure hope I'm not the only one seeing this too. On a seperate note, despite the aforementioned issue I'm happy Kaminsky showed up, honestly he's a god send (though I have a criticism for him specifically, I hope he won't mind, later in this post)

Second of all while I'm talking about development practices, why can't we make building Zandronum an easier task? Do you have any idea how terrible it is to set this port up for compilation, especially on Windows? Compare this now to GZdoom, which literally comes with everything pre-packaged and all I had to do was hit the build button on Visual Studio. That's it... THAT IS IT. That's how it should be! You either give me one "make" instruction to build and get everything, or give me a pre-packaged installation suite. Why are we still going with this "get this from here and that from here and mix this and that and set this and that"... Guys... Any self-respecting developer would FIRST make sure the target audience can get easy access to building their project. That's RULE #1. We need this. ASAP! You want more help? More developers? Do this. Hell I even contributed to GZDoom myself and to it's texture rendering code on screen, but not to Zandronum, and I refuse simply because of how hard it is to even set the damn thing up. Plus the codebase is a huge mess... but that's a different story entirely.

Third, still on the development side, I'd like to point this particular thing to Kaminsky. While I appreciate the countless help he has personally done for me and make my mod work (thank goodness he exists) I hate to say it: I feel like the development team is lacking clear direction. Yes. Why? Because, I don't know if anyone really is in favor of this feature, but voice chat has been a total waste of development time. I don't know why in 2025 anyone would use it on this port of all things, when Discord or any other alternative exists. Why would anyone want to use it? This feature cost many months to implement on top of the many crashes/little problems it brought. All for what? It's a luxury feature that isn't essential at all. Meanwhile there are major desyncs that affect gameplay SEVERELY (thankfully Kaminsky, the hero, fixed one of the longstanding ones. Again, thank you for all you do for the port man) but still please, have a clear LIST OF THINGS to add and order them! There are SO MANY severe crashes (P_PlayerThink spam I think still is happening in 3.2...) that KILL the joy of anyone playing.

Here's a scenario relevant: A major desync happens that makes your gun fire explosive rounds up close to a monster rather than the intended, normal rounds. Player dies. Frustrated, they DM me complaining about it. What can I do about it? The engine itself is literally malfunctioning even though the code at hand is completely sensible AND WOULD WORK IN OTHER PORTS JUST FINE. Here, online? Hell no. Online is supposed to be the BIG reason everyone comes to play this port, right? So why is it fucking dogshit, guys? I can't count the amount of times I've had to fix a monster or weapon related desync in Death and Decay simply because the port is either lacking WHOLE ASS client code (yes, looking at you stupid Heretic code pointers) or I don't know, someone half-implemented some code from years ago and it finally took me to find out it breaks. Great. Your greatest selling point is half-assed. Now what? You see my point here? FOCUS ON NETCODE STABILITY FIRST! Nothing else matters! You want players and modders to stay? Give them things they want, not some useless feature like voice chat that we have no access (probably won't, doesn't even make any sense... god forbid IT FUCKING DESYNCS LMAO) over either... I hope Kaminsky won't take offense to this part. I just want the best for the port, and capable hands are very few here. Time is also an incredibly valuable resource and what little time they have I should hope goes to the betterment of the port on more important things.

I'll address some of the things said in this thread now.

I personally really enjoy spending my time making things using the engine, even if it has some major limitations. But I do have to say, what point is there if it's possibly not going to be played anyway?

Me too, when it works... Trust me, I like the challenge of implementing highly advanced systems with many limitations in play... but nobody enjoys when their reasonable code FAILS RANDOMLY because of some random desync that shouldn't be there. It's extremely irritating, and literally puts many people off of doing incredible things with the engine.

Currently the main drawing power Zandro has over GZDoom is its multiplayer functionality, database support and maybe some specific features like Client-Side scripting. With the amount of contributors and pace of development that GZDoom receives, it could very well be on par with all of the aforementioned features in a shorter time frame than most people expect. People still wander into the Zan discord asking about Brutal doom coop because the experience is better on Zandro than what can be had with GZdoom. The question is, how long will that last?

Exactly. We can't keep betting on this being the case forever. When we can't even have MBF21 which is... I personally find it a completely unnecessary feature, mappers should just embrace UDMF and use DECORATE instead, but that's just me, anyhow, nowadays very prevalent.

Yes, but it's not easy, since we're tied down to an 11-year-old version of GZDoom. Implementing these features ourselves or backporting them would make it harder to update the GZDoom base in the future, especially because GZDoom has implemented them itself. Whether these features make it into Zandronum any time soon will depend on what we do for Zandronum 4.0.

It's too much work to implement? Well... I guess we won't be seeing any kind of player attraction anytime soon, maybe by the time we add MBF21 there won't be MBF9000 to fuck us over, I guess.

On a semi-related note, here a few things that have hurt Zandronum's community:

Lackluster community promotion and events from staff.
Social media age with no social media presence (bluesky doesn't count).
Little exposure to user created content
No hype anywhere

You can't attract new eyes if you don't put anything out there. Despite the Dark Ages, Doom is more popular than it was pre-2016 and Zan isn't doing much to draw from this burst of popularity. But I digress, since this topic is about port development.

I agree, and guys. The forum has been having lots of issues too. Recently this email issue that's been taking for some reason too long to resolve... And from what I remember the forum software being archaic isn't helping. We used to have lots of advertisement of community screenshots on the forums. Where are they? Where are the people making events? All gone? Oh bummer... No wonder the port is stagnant I guess. There's another reason. No publicity, no showcasing our features, no nothing. We are one step away from sacrificing innocent people for rain like Aztecs at this point...

I'm of the view that fixing that licensing issue should be the #1 goal for this project's longevity. You get this sorted out, you get more projects on steam and elsewhere rolling out with Zandronum. You get that going, then you get more active players. You get more active players, you get more contributors to the project. You get more contributors? Well now you're on a cycle to save this project forever basically.

Unbanning people, running community events, etc, is nice but these actions only attract people in our small Doom pond. They don't break this project out of the Doom bubble like MM8BDM did. That's what Zandro desperately needs. You gotta move away from the Doom bubble.

If you need a data-point I sincerely think freeing up this license is in everyone's best interest and should be the primary goal.

Community events, socials, updating the website does not benefit the project as much as freeing up the license does. If we free up the license people can just make standalone games of their own mods, run their own communities, upload their game on popular platforms, and breathe life into this wasteland more than any of that stuff ever could.

XSnake or Fused should be allowed to strip doom assets and upload his Zombie Horde 2 project on Steam.
Aenima should be allowed to strip doom assets and upload a rebranded Super Skulltag on Steam.
Cutman should be allowed to strip doom assets and upload GvH on Steam if he felt like it.
Someone should be allowed to strip doom assets, make their own weapons and maps, and create their own "Private CTF" onto Steam.
I should be allowed to strip doom assets and upload any of my mods onto Steam.

Do people understand what I'm getting at? Don't fall for the endless cycle of actions that just keeps this project inside the Doom bubble.

Absolutely! And this is not solely a discussion so that developers can make money either... Like this guy here thinks:

All this feels equivalent to commissioning an artist and offering to pay them in exposure. OK, Zandronum is more popular, now what? We still have a handful of developers with a small amount of free time to invest in the project, someone still has to pay for the infrastructure that deals with that increased popularity, etc.

Indie devs could contribute development time to the project? They could do that now! They could at least open a dialogue with us about fixing the licensing. But literally none of them have involved us at all. Again, it is well-known that the licensing situation is not that Zandronum's fault directly, it is fixable. I doubt they will involve us even if they could use the engine.
We could open to donations -- but plenty of FOSS projects see nothing while commercial endeavours exploit them. We can't force people to pay us (in money or otherwise) for using Zandronum commercially either.

Either way, it really sounds like that you don't have Zandronum at heart - it sounds like you just want your wallet to be thicker. It's unappreciative, and it's not a solution to solving the problems Zandronum actually has now. If, when I'm on my deathbed, you asked me what my life's greatest regret was - "Sgt Mark not being able to make 20 bajillion dollars off of my work" will not even remotely cross my mind.

Sorry but you either are very ignorant or purposefully being dense to not see the importance of lifting the license problems of this port. It will literally bring more people solely because they can publicize their work, be it for money or not. Thankfully nobody is going to ask you your biggest regret, because neither is it relevant to this discussion here nor does it have any significance. We are talking about Zandronum's best interest at heart, and it sounds to me like you're more focused on being on the spotlight yourself rather than letting other people do it. This is not about Random Guy 69 making 100 more dollars than you. This is about "Hey, look, there's an actual online doom engine that let's you make awesome games you play with your friends! Come, join us! Make amazing mods with the community helping you and enjoy the fun!" --- If for some reason you still don't get it after all these posts, then I must say I feel sad for the future of the port hanging on people like you holding it together. If I sound too harsh, sorry, but sometimes you have to say things directly rather than sugarcoat it. The facts speak for themselves.

Novellas? We used to write out more.

And how much did that accomplish...

I'm simply amazed at the fact that you don't remember the history of this port. Great moves and changes came from long posts of people confronting others about their lack of effort, responsibility... In general, need for change. And it accomplished its goal every single time. This is one of them. A call for change. Now you can either be part of it, or be against it. But the stagnation should exist no longer, otherwise more and more people will jump ship, and soon you'll be hosting the wiki for 1 person only.

Nobody’s saying Zandronum needs to become Unity overnight. But if we treat it like it never could be more than a Doom mod launcher, then yeah it’s going to eventually die out on a whimper. People like you have kept it alive this long, and that’s commendable. But keeping something alive isn’t the same as helping it grow. You don’t have to carry the burden of what comes next. But please, stop standing in the way of those willing to try.

Zandronum can NEVER become Unity, or Unreal. Nor does it have to. It just needs to be:

• 1. Easily Accessible
  2. Easy to setup
  3. Easy to enjoy online experience

Weren't those the primary goals of this port? Or am I in some alternate reality where we ditched all of this? It feels like with every update we stagnate and stray further from those instead.

You keep asking why devs haven’t come forward. I’ll answer plainly: because there’s nothing inviting them in. No modern docs, no discoverability, no presentation, and most importantly no legal green light to even ship a standalone game. And the few people who do try, like Sgt. Mark, hit legal roadblocks and walk away. That's not on them. That's on the engine failing to support ambition.

Very good point. I hope the port developers step forward to join this discussion as well, because this is a major issue as to why nobody wants to help develop for this port like we hope for them to.

Honestly there is so much more to be said, but I don't have all day to write more paragraphs. I only wish more people would step forward to voice their concern/thoughts about the matter. But before I finish...

I don't know about you guys, but I'd really like to not count birthdays of GZDoom versions forever, like Sean here... I'd rather this port adopted a much stronger and independant development strategy and stopped playing the catch-up game altogether, because it's 2025... Everyone else is moving on and this port is still stuck chasing after others. Remember the keyword: STAGNATION

On that note, GZDoom 1.8.6 is 11 years old today...

[Ru5tK1ng]

Which brings me to my first point: Please, move the repo to Github already. The years of stagnation and lack of anyone showing up to do anything for this port can easily be pointed at this being a strong factor. Most everyone who does any kind of serious Doom engine/modding development is on Github. It's easy to navigate, easy to use. Why don't we use it as well? I don't mean to sound disrespectful, but from what I heard this is due to Torr Samaho's preferences.

For what it's worth, there IS a Github mirror of Zandronum that's currently up to date, but it's so hidden away that barely anyone, who would be interested in it, knows it even exists: https://github.com/TorrSamaho/zandronum

It may not be the main development location of Zandronum, but it should be listed someone on the main site at least since apparently Pull Requests from the Github repo are accepted. Unfortunately, on our neglected stepchild of the milk man website, this information is nowhere to be found. I know you criticized the forums for being archaic, but the website, (and tracker to a lesser extent), suffers from the same issue.

Also, while it was true at one point in the past, it's not JUST Torr who has a preference to stay away from Github. From one of the horse's mouths:

because none of us like git
git is like a linus torvalds email: it's hostile, it's abrasive, nobody really wants to deal with it on a day to day basis

Second of all while I'm talking about development practices, why can't we make building Zandronum an easier task? Do you have any idea how terrible it is to set this port up for compilation, especially on Windows? Compare this now to GZdoom, which literally comes with everything pre-packaged and all I had to do was hit the build button on Visual Studio. That's it... THAT IS IT. That's how it should be! You either give me one "make" instruction to build and get everything, or give me a pre-packaged installation suite. Why are we still going with this "get this from here and that from here and mix this and that and set this and that"... Guys... Any self-respecting developer would FIRST make sure the target audience can get easy access to building their project. That's RULE #1. We need this. ASAP! You want more help? More developers? Do this. Hell I even contributed to GZDoom myself and to it's texture rendering code on screen, but not to Zandronum, and I refuse simply because of how hard it is to even set the damn thing up. Plus the codebase is a huge mess... but that's a different story entirely.

GZDoom is far easier to compile on Windows compared to Zandro. I ran into an issue the last time I had to make a Pull Request upstream to GZDoom, but thankfully it was a simple change that was documented on their forum. I have seen people struggle quite gloriously when trying to follow the strategy guide on the Zan Wiki and it's shame it's that much of a pain in the ass to compile. I know some dependencies can't be helped, but damn, it hasn't gotten any easier in the past decade to compile Zan. I know people always dunk on Odamex for one reason or another, but it's another example of how to properly lower the barrier of entry for potential contributors. When I dabbled with Oda some years back, it was a breeze to get it compiled, albeit not as easy as GZDoom. Odamex is set up so that you can pull the dependencies and even update them if necessary. This is in stark contrast to individually chasing download links for executable, header and library files.

As for the code base being a mess, part of that is simply a fundamental issue with Zan's source code design. You'll have to go back 20+ years to point fingers. But I think it's more productive to figure out ways to get people to fix it rather than just point the blame at you know who.

[Lollipop]

I'm not inclined to write carefully deliberated paragraphs here.
I will get to the point.


First order of business, the web presence:
The entire web presence of zandronum consists of:

• a website that looked ancient the day it came out
• posting on obscure social media nobody cares about

On top of that the website is so unmaintained that I will just encourage you to visit zandronum.com/credits and see for yourself.


Second order of business, compiling and running:
Believe it or not but the radical unfinisher here wanted to contribute at one point.

I can second the woes Ivan has mentioned about compiling, and that was on Linux which is supposedly easier. I gave up.
You can call skill issue if you want, but that won't change the fact that getting zandronum to compile is an exercise in black magic.
The Linux experience sucks ass as well for the simple reason it uses SDL1. Who the fuck does that in current year?
If an upgrade to SDL2 has happened since last I checked then let me know. I may actually bother downloading zandronum if I don't need to manually patch a library on my computer.


Third order of business, leadership:
Leadership of the port has been doing a very good job at making as many people as possible take their time and attention elsewhere.

I believe everything started with Torr explicitly not giving a fuck about the community side. He cares only about the code.
Let me ask, if the leader does not care about the holistic scope of the overall project, then how can he lead?
Fact of the matter is that zandronum doesn't have a defining vision. If it does then I would love to hear it.

On the administrative side I think it is unnecessary to dig into the history.
I'm also not a ST/zan history scholar so I'm also not the guy to ask.
However, I stand firmly by the stance that staff isn't a situation that has meaningfully improved.
The only thing that has happened is that activity is now so meagre that there is basically nothing to moderate, so the number of fuckups they can accomplish is near zero as well.
The only admin I have ever had a positive opinion of has been Mifu, and we all know how much that fucked with him.
People that actually want to be admins and moderators are generally not the people you want to have that power, and the people you want in power are usually those who resent the job.
That is really all you need to know to do a retrospective on zan staff.

As it stands currently, we see:

• features like voice chat coming out that does fuck all to motivate a modding scene in 2025.
• general staff doing fuck all to promote activity in the community.

Fourth order of business, conclusion:
Do I need to explain why the port is so fucking dead that even the usual suspects coming out of the woodwork to proclaim the A3 conspiracy aren't here?

If someone put a gun to my head and asked what the vision of the project is, and how it would be achieved I would die.
The lack of vision is obvious. It is a technical pet project as it currently stands, with fuck all with regard to any ambitions beyond that.
It is pretty darn evident because that is what we have seen the several years.

If this is how it is going to continue, then all that is left is to pick a date for the funeral.


Fifth order of business, the fuck to do:
It is plain fucking obvious.
Activity is the lifeblood of the port.
We want activity any fucking way we can get it if we want the port to survive at all.
What brings activity? Content.
Content is king.

There are two things you need for content to happen.
The first is that you need to make modding accessible, with powerful tools, good documentation, and ongoing development. Do not forget the bugfixes, as those are paramount.
The second thing you need is a community environment that is conducive to modders thriving. I can't explain this in short form, but it has certainly been fucked up.

If we want activity we need content.
To get content we need to make the modders happy.
To make the modders happy we need an actual vision for the future that we try to accomplish, and a great technical and social environment.
Zandronum has managed to consistently fuck up on all counts. Not always, but far too consistently.
Also doesn't help when the people who do a good job at these things burn out and give up.

There has already been great suggestions in this thread as to what to do.
Fixing the license issue will help, even if conversion rates are small from games that simply use zandronum as an engine. It would generate legitimacy in spaces beyond Doom.
Fixing bugs, particularly in the netcode is paramount. How long did turrets jitter erratically up and down on the base walls on AOW2? How long will we have to deal with the playerthink thing?
Making the project possible to compile without a master's degree in zandrology would help immensely in getting people to care about helping.
So would fixing the atrocious codebase. I know you picked up from the old carncode, but if it continues to be practically ancient hierglyps then you will be out of luck to get help.

However none of this matters if you cannot breathe new life into the modding scene.
Are we going to care about zandronum 4.0 when it comes out if there are no new mods to play? Of course not.
I don't know how you would resurrect the modding scene around here, except if you managed to gather a group of very nostalgic talents with enough fucks to give.
Enough fucks to put in a lot of effort continuously for several years for a total playerbase of 50 people at peak times.
I wish you good luck.
Spending those capitalist Great Briths Pounds towards that would be a better investment than what the money is spent on, so maybe consider that.