Free MMORPG Engine. Develop and host graphical browser-based games.
DimensioneX is a free Massive Multiplayer Game Engine.
It lets you develop and then run or host browser-based, graphical multiplayer games. The users will play games simply via their browser.
DimensioneX runs on any Java-enabled web server (eg. Tomcat)
Alien Battle Game Engine is a modular style game engine that will be able to make games in various different genres. It is programmed in the Basic4GL programming language.