Marauroa is a multiplayer online game framework server. It uses a multithreaded server architecture with a TCP oriented network protocol, a MySQL based persistence engine, and a flexible game system. The game system is totally expandable and modifiable by game developers and is able to run Python scripts defining the game's rules. Marauroa is based on a design philosophy called Action/Perception. Marauroa is totally game agnostic and makes very little assumptions about what are you trying to do, allowing a great freedom to create any game type.
webDiplomacy (previously phpDiplomacy) is a Web implementation of a popular turn based strategy game in which you battle to control Europe. It is not a game of luck: to win you must be diplomatic and strategic, forming and breaking allegiances and bargains with your friends and enemies. It features an interface intuitive and simple enough that seasoned Diplomacy pros and complete newcomers can play alongside each other.
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.
Arx Libertatis is a cross-platform, open source port of Arx Fatalis, a 2002 first-person role-playing game developed by Arkane Studios. Arx Fatalis features crafting, melee and ranged combat, and a unique casting system where the player draws runes in real time to effect the desired spell. The Arx Libertatis source code is based on the publicly released Arx Fatalis sources. This does however not include the game data, so you need to obtain a copy of the original Arx Fatalis or its demo.
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.
Slash'EM (Super Lotsa Added Stuff Hack -- Extended Magic) is a variant of the hugely popular roguelike game NetHack. It adds more monsters, more objects, more dungeon levels, more roles, and more races, shopkeeper services, and techniques for you to use, and invisible objects and gypsies for those who feel lucky. It also comes with a GTK windowing interface and higher resolution tile sets as options.