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)
EasyeMud provides a server, graphical client and a set of tools for creating and administering graphical online multi user dungeon (MUD) type games. Game content and logic are written in scripts similar to the Basicprogramminglanguage.