LDMud is an LP-class MUD engine, meaning it is object-oriented, with all object clases stored in unique files. The engine runs compiled bytecode to manipulate those objects, and the underlying simulated processor is a stack machine. It is a 3rd-generation LP-class MUD, being derived from Amylaar, which in turn was derived from the original LPMud. The game has no limitations on the nature of the game space other than the limits of your coding.
Cancan is a text-based, interactive utility similar to telnet, but with a number of extensions useful for MUD playing. Another use might be to provide line editing, aliases, etc., for those services that have a simple telnet interface. Cancan features aliases, actions, key bindings, text highlighting, substitutions, and line editing with history and completion.
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.
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.
JamochaMUD offers Unicode, plug-in, and multi-language support (8 different languages) to allow a more enjoyable MUCKing/MUDding experience. It features command history, synchronized window controls, experimental SOCKS 5 support, and greatly improved ANSI colour support. It plays nice on Unix systems, supports a wide range of MU*s, and also includes emulation of some TinyFugue editor controls. JamochaMUD includes classes that may be easily reused in other Java applications.