The ioquake3 community effort to continue supporting/developing id's
Open-source engine for Heroes of Might and Magic III
Multi Theft Auto is a game engine
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Voxel game-creation platform with easy modding and game creation
Real Time Strategy game engine supporting early Westwood classics
dhewm 3 main repository
Open source clone of the Age of Empires II engine
Recreation of the classic Grand Theft Auto III game executable
RPG Maker 2000/2003 and EasyRPG games interpreter
Descent 3 by Outrage Entertainment
3D Procedural Game Engine Using OpenGL
An OpenGL RTS game engine written in C
Orx: Data-Driven Game Engine
A modern, cross-platform Quake game engine based on FitzQuake.
GemRB is a portable open-source implementation of the Infinity Engine
Game engine supporting many 3D/2D formats and graphic effects
An isometric arcade-style game of skill, puzzles and exploration
A cell-based puzzle game featuring classic and completely new puzzles
utility collection for 2D game development in Java; sound-player
RTSish Game Engine
ZDoom 2.8.1 fork focusing on modernisation, performance and stability