CoffeeMud is a text-based virtual reality game engine (a MUD). It is a mature, full-featured Java codebase. It includes web (HTTP) and email (SMTP) servers, chat (IMC2 and I3) and web clients, and supports ANSI, MXP, and MSP.
A 3D game engine in java. This game engine should be usable by anyone that want to create 3d game in java without having to use vbo, shader or direct call to opengl. This api most be easy to use and efficient.
A browser game framework implemented with Grails. The goal of Little Goblin is to create a game engine that allows you to "just add content" and you will be able to host a game that is only limited by your creativity.
Free MMORPG Engine. Develop and host graphical browser-based games.
...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)