The Tiny JavaScript Game Engine That Can!
Open source library for creative expression on the web, desktop, etc.
Full featured MUD server with all the trimmings.
A 2D rigid body physics engine for the web
The multiplayer game engine
MIT Licensed Open Source version of Torque3D from GarageGames
Turbulenz is a modular 3D and 2D game framework
Educational framework for OpenGLES, OpenCL and OpenAL
2D physics engine for games
Java Client + JS/Canvas Server-Side System, with maintained Objects
Demonstrating the features of jMonkeyEngine 3.
Free MMORPG Engine. Develop and host graphical browser-based games.