Vallheru is a turn-based, fantasy MMORPG written in PHP and MySQL (but may work with many other databases) with Smarty Template Engine, ADOdb, and PHP Mailer. It is based on Gamers-Fusion 2.5 with many modifications in security, speed, and features. It is currently available only in Polish.
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.
GNU FreeDink is a portable and enhanced version of the Dink Smallwood game engine. It aims at running the original game as well as its D-Mods (Dink MODules, or add-ons), with close compatibility, under new platforms. The internals of the engines are being cleaned up to allow for portability and later improvements.
L2J is an alternate game server for Lineage2. The L2 protocol is reimplemented in the server, so you can play with this server without any modifications to the client (except changing the server IP address). The latest USA live client version is always supported, so don't expect this server to work with the PTS/Korean client.
PCGen is a Java (1.5+) -based character generator aimed at supporting OGL role playing games like those based upon the SRD, RSRD, and MSRD (such as Dungeons and Dragons). It is highly configurable by the users, allowing the Game Master to add or remove races, classes, feats, etc., and to implement house rules such as differing class or race restrictions. Level advancement is also supported, with configurable progressions of feats, skills and ability score bonuses. For "at the table" support, PCGen offers a set of GM plugins. Further options allow the user to produce a customized character sheet, which can then be viewed in, or printed from, the user's WWW browser. It can also produce a "party" sheet with the information needed by the GM.