ZDoom Licensing

Does anyone know how ZDoom is licensed? I've heard rumblings that it's DSL or BSD or GPL or lots of different licenses... but I just have no idea and the last time I checked their codebase it wasn't clear.

Perhaps read the documentation that comes with ZDoom?

The original Doom source code was released by id Software under the
Doom Source Code License. See doomlic.txt.

Parts of the renderer use code from the BUILD engine by Ken Silverman.
See buildlic.txt.

The majority of original code uses a BSD-like lincese. See bsd.txt.

This software is based in part on the work of the Independent JPEG Group.

This software uses the 'zlib' general purpose compression library by
Jean-loup Gailly and Mark Adler.

This software uses the gdtoa package, see gdtoa.txt.

This software uses the snes_spc library, which is covered by the GNU Lesser
General Public License. See lgpl.txt.

This software uses the "Dynamic Universal Music Bibliotheque" library for
MOD music playback. See dumb.txt for original license. The version used,
however, has been heavily modified from its original form and is the same
version used by the foobar2000 component foo_dumb as of mid-2008, found at
http://kode54.foobar2000.org/.

This software uses the OPL emulator from MAME 0.95. Playback of MUS files
on the OPL emulation is accomplished with some help from Vladimir Arnost's
MUS File Player Library, with fixes to make it more accurate.

Basically, it's a mish-mash of everything under the rainbow. I don't know much about the GPL relicensing though (or how it was done), except it was for the sake of Odamex.

EarthQuake said:
I don't know much about the GPL relicensing though (or how it was done), except it was for the sake of Odamex.

If I am not mistaken, the relicensing was for ZDoom 1.22 code in CSDoom base which was already demanding to be under the GPL due to QuakeWorld code. It implied removing any code not compatible with the GPL.

Well I read that file, but aren't there (severe and irreconcilable) compatibility issues between BSD, the BUILD license, the DSL, and the LGPL? I mean I'm not trying to attack ZDoom or cause a commotion, and I'm sure this is probably something that's been hashed out many years ago, I'm just confused that's all.

EDIT:

OK the Doom Wiki links the wrong DSL. It links the license that came with the Doom binary distribution, not the one that came with the Doom source distribution. The important part of the real DSL is here (again emphasis mine):

4. Copyright. The Software and all copyrights related thereto
(including all characters and other images generated by the Software
or depicted in the Software) are owned by ID and is protected by
United States copyright laws and international treaty provisions.
Id shall retain exclusive ownership and copyright in and to the
Software and all portions of the Software and you shall have no
ownership or other proprietary interest in such materials. You must
treat the Software like any other copyrighted material. You may not
otherwise reproduce, copy or disclose to others, in whole or in any
part, the Software. You may not copy the written materials
accompanying the Software. You agree to use your best efforts to
see that any user of the Software licensed hereunder complies with
this Agreement.

I mean I'm not a lawyer, but it looks like the license forbids distributing the source yourself, which ZDoom clearly does. Then again I don't know what they really mean by this clause:

2. Permitted Uses. For educational purposes only, you, the
end-user, may use portions of the Source Code, such as particular
routines, to develop your own software, but may not duplicate the
Source Code, except as noted in paragraph 4.

...because paragraph 4 gives no rights of distribution whatsoever (it's above). As far as I understand it, this means you can distribute your executables that you created using the source code in an "Educational" manner, or even the source for those executables as long as you didn't copy the Doom source into your program. You just can't distribute the Doom source itself. If you copied the Doom source into your program, you can't distribute the source for it.

Ladna said:
I mean I'm not a lawyer, but it looks like the license forbids distributing the source yourself, which ZDoom clearly does. Then again I don't know what they really mean by this clause:

It sounds kind of scary but the words "you may not otherwise" are counter-indicating something; you may not reproduce or copy it except as id Software's copyrighted materials. Section 2 explains how to copy any parts without infringing their copyrights. Carmack's notes on the other text file start with: Here it is, at long last. The DOOM source code is released for your non-profit use.

One thing that is even more limited, that isn't mentioned in the ZDoom text file nor included in the licenses package, is the license for Raven Software's games. It's the license included with the games; any resulting mod can only be used with the game it's from. This would exclude using Hexen sources for DOOM, for example.

myk said:

It sounds kind of scary but the words "you may not otherwise" are counter-indicating something; you may not reproduce or copy it except as id Software's copyrighted materials.

I think I agree with you. I mean, you can't do that anyway; you can't copy a copyrighted work, it's illegal, but I think I still agree with you.

myk said:

Section 2 explains how to copy any parts without infringing their copyrights.

OK I think I agree with this too. It's saying that you can copy the "Source Code" as long as Id Software retains the copyright (and it would anyway without an explicit transfer).

Really it's a very strange license. Why would you redundantly assert your copyright rights in paragraphs 2. and 4., and why would you grant users the right to distribute derivative, non-commercial works in such a roundabout way in paragraph 4.? I tentatively agree with you that the general aim of the license is to allow non-profit use of the software while still retaining ownership and copyright, but they sure do it in a weirdo way. Antecedents, sometimes they're not as obvious as you think they are.

Anyway, thanks for clearing it all up for me guys. I appreciate it.

Ladna said:
I mean, you can't do that anyway; you can't copy a copyrighted work, it's illegal, but I think I still agree with you.

You can, if the author lets you. All sources under the GPL are still copyrighted to any corresponding authors, for example, but they've licensed them so that users can do certain things with them.

In the other thread, Quasar was saying it's okay that the ZDoom coders use his polyobjects code as long as they release derivatives. There he's exercising his copyrights over that code, which he licensed under the GPL. If the GPL negated his rights, and it were not still his copyrighted work, he could not do something like that. Another coder using Eternity code, for example, couldn't give the ZDoom team those permissions, because they don't have copyrights over it, just a license to use it in some ways, passing derivatives only in its terms.

The DSL looks much like many other software licenses. They try to write things in a way that can avoid as many ambiguities that may prejudice them, or interpretative exploits, as possible.

ZDoom is under the don't-give-a-shit license.