Cooperative multiplayer graphical RPG and adventure game
Crossfire is a free, open-source, cooperative multi-player RPG and adventure game. Since its initial release, Crossfire has grown to encompass over 150 monsters, 3000 areas to explore, an elaborate magic system, 14 races, 16 character classes, and many powerful artifacts scattered far and wide. Set in a fantastical medieval world, it blends the style of Gauntlet, NetHack, Moria, and Angband.
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
Starlight is a MMORPG written using Ogre3D and PyGame in Python that focuses on role playing, player modifiable worlds, strong computer artificial intelligence, and peer-to-peer networking.