Source of Mana is a unique 2D MMORPG
Cooperative multiplayer graphical RPG and adventure game
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
Open source voxel world
An online multiplayer real time strategy game
This lets you create worlds more easily and to recreate a world
Computer-assisted miniature tank game.
Build increasingly complex rail networks on an infinite world.
Grepolis utility
Converts Minecraft world files between formats to allow editing
Positional Audio Communication for Minecraft with Mumble
A fantasy real time multiplayer strategy game with player scripted AI
Tongue-in-cheek action RPG
Minecraft side viewed game made in Java
The original Xivio.com World Server Core
Unique web based space strategy game written by Andras Nemeth
A mod for Civ4 Beyond the sword
Open Source Virtual World and MMOG Development Platform
EPIC is an indepth Multiplayer Strategy RPG Web Game
A 3D multiplayer RPG based in the world of Khoras.