GemRB is a portable open-source implementation of the Infinity Engine
Orx: Portable Game Engine
Action RPG that's easy to mod
General Purpose Engine for Graphic Adventures.
A free 3d game for PC that does not limit the player. Fight,Build,Gain
functions for 2D/3D graphics + realistic driving simulation
SDL based generic 2D game engine
2D Open Source MMORPG
A roguelike, contains binaries and source packages for
A cross platform Lua based game engine
Opensource Game Studio
scriptable game engine with built-in support for 2D graphics and sound