Arianne is an engine to develop multiplayer online games like Stendhal
...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
OpenRTS is an open source realtime strategy game. It features isometric graphics, networked multiplayer and single-player scenarios. The game is being developed using Python and SDL. The game runs on at least Linux, Windows and Mac.