Godot is a powerful cross-platform game engine
Real Time Strategy game engine supporting early Westwood classics
Open source HTML5 game framework that offers WebGL and Canvas
Gideros Release version
Self-hosted CMS platform based on the Laravel PHP Framework
ThinkPHP Framework
Open Source MMORPG Framework
Arianne is an engine to develop multiplayer online games like Stendhal
Old-school 2D game engine
Game engine supporting many 3D/2D formats and graphic effects
Amateur 3D Game Engine
JavaScript framework to build game engines, games, emulators and apps
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
FreeCS is a free-software reimplementation of Counter-Strike 1.5.
The imaginary eight-bit machine
Free and Open Game Programming Language for Windows and GNU/Linux
Asphyre is a cross-platform framework for Delphi and FreePascal.
2D game engine for traditional platform games
Open Game Bootstrap
Built to be ease of use, with no programming knowledge, Multi-platform