An Open Engine for use on the OUYA
An extensible development framework for roleplay games.
CoffeeMudForAI is plaform to design AI in
A java-based, purely object-oriented chess engine.
Modular Minecraft server plugin - commands, events, ...
Unless you're getting started in Java, you probably don't want this.
A Java Tic Tac Toe Game
Game Mode API for Minecraft