Desktop/Android/HTML5/iOS Java game development framework
A simple cross-platform game engine for creating old-school 2D games
Arianne is an engine to develop multiplayer online games like Stendhal
Java Settlers
8-bit Graphical API for Java
Source code of the chapters of the book 3D Game Development with LWJGL
Example code for creating a 2D platform game in Java.
Free strategy browsergame engine.
MultiLingual Interactive Fiction
Open Source Virtual World and MMOG Development Platform
A game engine in java for 2D strategy games
AMOS BASIC reimplementation in Java
The next generation mud is an open-source extensible, programmable mud