Open Source MMORPG Framework
ThinkPHP Framework
You can make it - Open Source MMORPG Platform
Arianne is an engine to develop multiplayer online games like Stendhal
Java Settlers
Cinema Enters Game Console
Asphyre is a cross-platform framework for Delphi and FreePascal.
A starter development kit that let you develop FF6-like games on PC.
3D .NET engine for Windows, Linux, Mac
AutoTeach makes kids study and learn in exchange for internet access.
Pear3DEngine is a modern and modular 3D development framework
An extensible development framework for roleplay games.
An HTML web game platform
Cross-platform 2D game engine
Game framework on top of Python, Panda3D and Twisted
Atlarius is no longer under development.