Is Skulltag open source?
• No, the sources are not available to the public. • The Doom source code was originally released in 1997 under a proprietary license that does not require to provide the source code for modifications released in executable form. ZDoom is based on the original source code release and therefore falls under the same license. ZDoom even is incompatible with the GPL, because it contains parts of the Hexen source that only was released under a license that is not compatible with the GPL. Skulltag uses the same license as ZDoom, so there is no legal obligation to release its source. • The fact that the Doom source was re-released under the GPL in 1999 has no influence on the release under the original license.