GemRB is a portable open-source implementation of the Infinity Engine
Cooperative multiplayer graphical RPG and adventure game
DOOM / Heretic / Hexen source port with enhanced graphics and UI
ZED OS the clone of Windows XP
Ubuntu-based Linux Gaming OS
A Graphical Launcher for Mupen64Plus
Cross platform 2D game creation framework with Python bindings
A powerful cross-platform and open-source 3-D rendering engine.