Crossfire is a multi-player graphical arcade and adventure game made for X. It has certain flavours from other games, especially Gauntlet and the rogue-like games (Nethack, Moria, Angband, and Ragnarok). Any number of players can move around in their own window, finding and using items and battling monsters. They can choose to cooperate or compete in the same world.
The Interreality project is a collection of Open Source, Free Software projects based on the Virtual Object System (VOS) platform. The goal is to develop a free and open platform for multi-user 3D virtual reality games, applications, and interactive, collaborative 3D virtual spaces. VOS is a powerful and generic network object framework designed to support a variety of high-performance applications. It is the basis for Ter'Angreal, a general-purpose browser application for entering and participating in 3D worlds.
Deliantra is an advancement of the crossfire multi-user RPG game. Unlike the original project, it focuses mainly on stability and playability, but also adds modern technology such as map scripting, Perl server extensions, asynchronous I/O, higher resolution graphics, and better client support.
AIME is a C++ MUD engine with an OO design, designed to provide utmost flexibility for the designer to create complex worlds. It has a fully-functional builder port, online interpreted specials code, and a flexible levels/quest/profession track system to allow the game owners to set up any world they can imagine.
Phaos is a browser-based MMORPG. It features character creation, the ability to purchase/sell/drop potions, weapons and armor, traveling, inter-player chat, the ability to fight in the arena, explorable dungeons, an admin system, the ability to trade with other players, and the ability to fight other players. A download is available for people running Windows who do not have access to or do not want to set up a Web server.
MV3D is a virtual world and multi-player game framework for use with Python. It was designed with scalability in mind and is able to distribute a world across as many servers as needed while dynamically balancing the load. The simulation framework is not specifically slanted towards any one genre of online game or virtual world, and can just as easily be used for a space game as a fantasy setting. Objects on an MV3D server can be simulated using the ODE physics engine for realistic interactions. A single server is able to host thousands of of simulated objects. The client works with both the Ogre3D and Panda3D renderers.