Arianne is an engine to develop multiplayer online games like Stendhal
...The engine Marauroa provides a simple way of creating games on a portable and robust server architecture. Marauroa manages the client server communication and provides an object orientated view of the world for game developers. It handles database access in a transparent way to store player accounts, character progress and the state of the world
JSettlers2 is a web-based version of the board game Settlers of Catan written in Java. This client-server system supports multiple simultaneous games between people and/or AI bots. Originally written by Robert S Thomas as an AI dissertation (http://sourceforge.net/projects/jsettlers).
The active source code is hosted at https://github.com/jdmonin/JSettlers2 including full history; the sourceforge CVS is historical up to 2012-09-28.