3D game engine/framework in C, with Luajit and Python bindings now
Full featured MUD server with all the trimmings.
Multi-platform game engine similar to old Megaman with a stage editor
A 3D game engine in java.
A truly extensible cross-platform game engine
Game engine supporting many 3D/2D formats and graphic effects
Free MMORPG Engine. Develop and host graphical browser-based games.