RetroArch is a frontend for emulators, game engines and media players.
RenderDoc is a stand-alone graphics debugging tool
A dead simple 2D game library for Go
Free 32/64/16-bit multi-platform Pascal and Object Pascal compiler
Cerberus Content Management System
Game engine supporting many 3D/2D formats and graphic effects
An open-source Phantasy Star Online server for *nix
A promising chess program
3rd Party Video Games Developer: MetalManGames, titles of games
Web IDE in single HTML file
Run STM32 with simple examples
Machine Language Monitor for Commodore VIC-20
2D Game Engine
A homebrew video suite for game consoles
Game backup loader for Wii and vWii
Run Linux on the Playstation 2
A cross-platform interpreter for many point-and-click adventure games
Android, DOS, FirefoxOS, Linux, MacOS and Windows all in one..
Paintown is a 2d fighting game engine.
Portable Pokémon Mini Emulator
Cross platform Game Creation Software