Legalities of using ZDoom (or other sourceport) for commerce

[darkhog]

I'm thinking about using ZDoom in a commercial game at a later, undisclosed, date. The situation would be kinda similar to how originals are distributed - the engine would stay opensource, however you'd have to buy wads themselves. It would also contain no resources from Doom, Hexen and so on and instead would have its own. But I wonder how legal would it be? I mean, GPL allows for commercial use, and this setup worked for original Doom and Doom 2 for years...

In any case, Doom engine would be a nice engine for an indie FPS, don't you think?

[Caligari87]

Unfortunately the licenses used in ZDoom and GZDoom are NOT compatible with commercial exploitation, so you may NOT use the stock engines in a game you plan to sell.

However, there is an on-going attempt to rectify this with GZDoom-GPL, and GLOOME, both separate projects with slightly different focuses. Personally I'd recommend looking into GZDoom-GPL.

[darkhog]

Isn't ZDoom GPL'd as well? Also I reeeeaaaaally want a software renderer, not that opengl thing which just makes Doom messy. :/

[Nash]

Have a look at [wiki]License[/wiki] for detailed information regarding what licenses are used inside ZDoom.

If you want to use the software renderer for commercial purposes, you're going to have to remove every BUILD-related code from the renderer and roll up your own replacements. Then you also have to get rid of FMod and the OPL subsystem.

People have suggested "workarounds" by selling only your IWAD and require your users to download ZDoom by themselves but this may be considered an exploit. The best course of action is to talk to a lawyer before doing anything.

[darkhog]

Don't know if you know, but FMOD went free for indies some months ago, so I wouldn't need to remove FMOD. And yeah, I probably wouldn't use voxels or slopes myself (and if I end up needing either of those, there's so much docs on these nowadays that I could implement them myself) anyway so removing BUILD parts could be done easily.

[Nash]

ZDoom uses FMOD Ex, which is not listed as free on the FMOD sales page.

[darkhog]

FMOD Commercial License

1. All commercial use of FMOD requires a Commercial License (even with free Indie license). contact Sales for more information.

Emphasis mine.

[Nash]

... okay? So all the more reason to remove FMOD then, what you said "so I wouldn't need to remove FMOD" is wrong then.

[darkhog]

Even. With. *Free*. Indie. License.

All I have to do is to contact their sales dept to obtain one *free* indie license which I'll do when it's time to start that project.

[Caligari87]

But you still need to remove the non-GPL Build and OPL code from ZDoom. Since the software renderer especially relies on the Build source code for many, many things, this is not an easy task. Until you can do that, ZDoom's software render cannot be used for commercial games.

Besides, the OpenGl renderer can look very close to the software renderer with some setting changes, and provides many more features. You're best bet is to use GZDoom-GPL.

[Nash]

darkhog: Calm down. If you want to contact Firelight then that's your choice. I'd rather just get rid of their code and wash my hands clean. :) But as Caligari said, that's only a portion of the problem. The software renderer is a huge block that prevents ZDoom from being used commercially.

[darkhog]

Build code AFAIK is only used for slopes, decals and voxels, neither of which I really need for that project (and some of which I can easily recreate myself).

[Graf Zahl]

Wrong. Build code is littered throughout the rendering code, even some of the low level assembly routines. The bottom line is: You cannot use the software renderer for any kind of commercial purpose.

Strictly speaking, you also cannot use FMod with GPL'd code, even in a commercial project because GPL does not allow linking to closed source libraries.
You also cannot use the code commercially under any other license because there's no license attached to the original Doom, Heretic and Hexen code that would allow it.

What you legally CAN do, is use a version of GZDoom that's free of all code with a non-commercial and/or closed source license, but that'd mean OpenGL only, no OPL music and no FMod. And that's the only legal way to use ZDoom commercially.

[darkhog]

Do you know of any other source ports that use software renderer and aren't a licensing nightmare? Again, I'm fine with GPL'd code since that just means I have to open the engine itself while having ability to sell wads with engine attached.

[quote=Caligari87] the OpenGl renderer can look very close to the software renderer with some setting changes[/quote]

Close!=the same.

[maseter]

What if he only sells the wad, and the installer downloads GZDoom, that's not redistributing?