DimensioneX is an easy, free multiplayer (MMORPG) game engine. It is a software for developing and running multiplayer adventure games.
Once you have it working on your PC you can easily develop a web-based massive multiplayer game with the scenes and characters you like. Develop your dream game and invite friends to play!
DimensioneX runs on any Java-enabled web server (eg. Tomcat)
Download: http://sourceforge.net
Website: http://www.dimensionex.net