UCI chess engine
Multi Theft Auto is a game engine
Cross-Platform C++ 2D/3D game engine
Open-source engine for Heroes of Might and Magic III
Free game engine for development of desktop, mobile, and web games
Source code repository of the FreeOrion project
A game of dungeon exploration, combat and magic
A free Chess program for Windows with a large set of features
Grow a Garden Script - Auto Farm, Infinite Seeds, Sell All
A LinuxSampler Qt GUI Interface
A Sudoko Solver/Puzzle Generator For MS Windows
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
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
A 2D game engine and level editor
A SaveGame & Mii Manager for the Wii
Most elegant 2048 puzzle with game fields 4x4 8x8 16x16 for Windows
Game backup loader for Wii and vWii