UCI chess engine
Open-source engine for Heroes of Might and Magic III
Multi Theft Auto is a game engine
Cross-Platform C++ 2D/3D game engine
Source code repository of the FreeOrion project
A game of dungeon exploration, combat and magic
Free game engine for development of desktop, mobile, and web games
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
Grow a Garden Script - Auto Farm, Infinite Seeds, Sell All
A LinuxSampler Qt GUI Interface
A Sudoko Solver/Puzzle Generator For MS Windows
Tools for Super Tux Kart server operators
RTSish Game Engine
GUI for downloading/managing homebrew apps for video game consoles
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
3D C++ Game Engine - yet another open source game engine
finds the sortest path on the square board. GUI is implemented in Qt.
2D ARPG Engine
Play any MIDI song on floppy drives !
Turn based Civ-like strategy game
Open Game Bootstrap