Free game engine for development of desktop, mobile, and web games
Cross-Platform C++ 2D/3D game engine
Edit BZFlag world maps with 3D preview
Free, powerful, and undetected Brookhaven RP script for Roblox.
RTSish Game Engine
Tools for Super Tux Kart server operators
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
3D C++ Game Engine - yet another open source game engine
2D ARPG Engine
GGMud is a cross platform modern MUD client.
Turn based Civ-like strategy game
Karaoke effects creation tool with ASS and Lua.
A GUI Level Editor for the Enigma Game