dhewm3 - dhewm 3 is a Doom 3 GPL source port, known to work on at least Windows, Linux, macOS and FreeBSD.
fhDOOM - Modernized DOOM3/idTech4 engine: ported to modern OpenGL (core profile), enhanced visual effects, improved performance, improved editor, more to come
Doom - Doom is a science fiction horror-themed first-person shooter video game in which players assume the...
GZDoom - ZDoom is a family of enhanced ports of the Doom engine for running on modern operating systems.
Freedoom - Freedoom is a WIP a complete free content game based on the Doom engine.
Anarch - Suckless, anticapitalist, public domain game for everyone