ZDoom/gzdoom

UZDoom is a feature centric port for all Doom engine games, based on GZDoom, adding an advanced renderer and powerful scripting capabilities

Easily portable doom

Chocolate Doom is a Doom source port that is minimalist and historically accurate.

Improved version of the X-Ray Engine, the game engine used in the world-famous S.T.A.L.K.E.R. game series by GSC Game World. Join OpenXRay! ;)

Freedoom is an entirely free software game based on the Doom engine.

Vulkan Quake port based on QuakeSpasm

This is the primary repository for collaborative efforts between Doom developers on Project Brutality. This is the bleeding-edge version that is constantly being developed on, and not meant in any way shape or form to be representative of the final version of the mod.

DOOM Open Source Release

Doom 3 BFG Edition