Gloome: A Standalone, Commercial-Friendly GZDoom

id Software may have released Doom‘s source code years ago (the old one, not that new one obvs), but it’s not quite as free as you might expect. With some of the most popular modern versions of Doom using bits of licensed code and reliant on Doom data files, folks have been uncertain whether they’d be able to release proper standalone games – which still has a big and creative modding community.

Enter Gloome, a community project to remove and replace bits that are potentially legally troublesome and enable standalone GZDoom-engine games.

The community-updated engine GZDoom (and its parent ZDoom) is the foundation for a lot of modern Doom development, but includes bits of licensed code from all over the place. Even if folks making a new game on the engine replaced every art asset and sound and whatnot, they still wouldn’t be legally clear to release it. Gloome clears up all the questions about releasing standalone games by removing, rewriting, and replaced all troublesome code. It should also make things far simpler to play. The project’s creators explain:

“Someone completely unfamiliar with Doom, the Doom modding scene, or anything at all can just download a game, fire up the .exe, and play it without needing any know-how or “drag this .pk3 onto this .exe” or “load up multiple files” or “DON’T PUT IT IN YOUR SKINS FOLDER FOR THE LOVE OF GOD”. If somebody wanted to make a full-fledged indie first-person-shooter, they can use this engine to create a slew of new maps, new enemies, new levels, new items, new weapons, and more, and then throw it up on Steam without worrying about Doom copyrights.”

Good stuff, that.

“But what does this mean for me?” you may ask. Well, if you’re lucky, we’ll have standalone games coming based on that dear engine. Gloome project lead ‘marrub’ is already working on one, named Nocturne in Yellow, as you can see in the project’s ZDoom forum thread.


  1. Spacewalk says:

    A Freedoom screenshot might’ve been more fitting.

  2. jmtd says:

    Erm… There’s some serious confusion here.

    Gloome is based on GZDoom is based on Zdoom, which is the point at which legally troublesome code was added (stuff from BUILD, Heretic/Hexen, etc.)

    That stuff was not present in the original doom source code that was released by ID.

    Gloome also appears to be taking GZDoom and changing the license to GPL, and it’s not clear that they have sought the permission of the original authors, so this is, if anything, even more legally troublesome than when they started.

    If you really want to build a new Doom-engine game without any legal concerns you could use Chocolate Doom, or Prboom, which are both fairly faithful but modern and entirely GPL; or Doomsday with its fancy graphics etc.

    • Alice O'Connor says:

      Ah, heck! Thanks for the clarification.

    • jrodman says:

      Are they creating a collected work under GPL, or marking all the source code files as covered by GPL? The former is totally reasonable, the latter is extralegal.

    • The_invalid says:

      jmtd – Your interpretation here is a bit off-base.

      Gloome’s aim is to strip out and re-code all the parts of G/ZDoom that weren’t broadly GPL-compatible. It hasn’t taken anything and ‘changed’ it to use GPL – the only code in it is either original, or reused under three main applicable licenses – GPL for original Doom code, 3-point derivative BSD for ZDoom code, and LGPL for GZDoom code, all of which do not require consent or permission from the original code authors, as long as the redistribution terms are met, which they are doing.

      • jmtd says:

        Hi, thanks for replying. This is probably not the right place for a debate, but just to say I’ve been following the Zdoom license situation for a long time (over ten years). I’m afraid I think you have interpreted it wrong. For a start, there is no GPL code in Zdoom. Not even Fragglescript. link to is a good starting point. The doom code in Zdoom predates it being released under the GPL. Code derived from the Doom code can not automatically be re-branded GPL without any other copyright holders consent (everyone who has modified it). This commit to GLOOME (–/GLOOME/commit/17f3b83087f153780d7ca4dc78a6ee5000236cbe) is a straight up replacement, which does not clearly indicate that permission for relicensing was obtained from all authors. In short, given the goals of this project, the situation is far from clear cut or confidence inspiring for any indie game authors who might want to build on it. I’d love this to be done right.

        • meris_keppler says:

          Remember that the Doom source code was re-released under the GPL. While Zdoom’s implementation of Doom code was before the GPL re-release, there is nothing saying that the Doom code in this fork was not taken from the identical re-release or is exempt from using the GPL re-release license. Saying that it does based on just the parent fork using a different license strikes me as, well, not very solid…

          While this definitely is not the right place for a debate on licenses, to me this instance checks out fine. Otherwise, we’ll find out in a week or month when this inevitably reaches Bethesda. :)

          • meris_keppler says:

            Sorry, when this reaches Zenimax. I keep forgetting that Bethesda is the subsidiary, which really shows how much I play their games.

          • jmtd says:

            Sure, if the code was unmodified, then you could call it GPL and you’d be fine. But Randi’s changes to the Doom code, and others, aren’t automatically also GPL too. They’ve never given out the zdoom source and said ‘this is GPL’. (Some of Randi’s changes predated the relicensing too).

            I doubt Zenimax will go after this at all. But if I was an indie developer thinking of making a game and selling it for money, and based it on this, and was moderately successful, *then* that’s the point to worry.

          • meris_keppler says:

            They have given out the ZDoom source. It’s BSD.

        • The_invalid says:

          meris_keppler kind of got there before me, but yes – As far as I understand, any use of Doom code after the GPL release was effectively dual-licensed. Now I don’t profess to knowing the subtleties and technicalities of how all these different licenses interact with each-other, so I could be entirely off-base here, but I was fairly sure that BSD and derivative licenses were broadly GPL-compatible and didn’t preclude commercial use.

          If I’ve totally misinterpreted that, then please do let me know. I was kind of fixing to use Gloome for a small game project, and it would be good to know if I could put it up on, say, Itch without the ZDoom guys lawyering up at me :P

  3. Snids says:

    It’s name reminds me of the lovely GLOOM on the Amiga. Sweet memories.

    • Excelle says:

      I logged in to post this, and you beat me to it. Here’s some screenshots for your memories (and for other people’s benefit!):

      link to

      • Spacewalk says:

        I don’t think that those intermission screens could get any more nineties than that despite each of the characters having no more than four pouches max and not nearly having enough ridiculously overdeveloped muscles.

    • Spacewalk says:

      Actually, I thought this was going to be a version of the Quake 2 mod done for Doom.

  4. Cantisque says:

    Just what we need. A flood of “DOOM-inspired” clones hitting Steam from amateurs.

  5. bbcisdabomb says:

    Three days late and pretty minor, but Nocturne in Yellow is being made by Terminusest13, the guy behind Demonsteele. marrub is making Project 67, a different game that looks more like a standard Doom shooter.

    I wouldn’t have said anything, but Term’s a really cool guy and any plug for Demonsteele is a good thing.