Desktop/Android/HTML5/iOS Java game development framework
Arianne is an engine to develop multiplayer online games like Stendhal
Java Settlers
Source code of the chapters of the book 3D Game Development with LWJGL
8-bit Graphical API for Java
Example code for creating a 2D platform game in Java.
AMOS BASIC reimplementation in Java
The next generation mud is an open-source extensible, programmable mud