Lich is a cross-platform multithreaded interpreter meant exclusively for use with text-based MUDs. Its primary goal is to provide a dynamic and extensible framework that offers advanced users the ability to customize the application and its functionality to their needs while remaining accessible and useful to the majority of players. It supports scripting in Ruby, Simutronics "Wizard", and, in Unix environments, any language with an interpreter program.
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.
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.
Deliantra is a client for Deliantra game servers. It offers an intuitive user interface for exploring the vast game world, a persistent minimap, powerful macros and keymaps, dialog-based NPC interaction, and easy configuration for the skill, spell, and item system. It is based on Perl, SDL, and OpenGL for high performance on modern systems, and works on both Unix and Windows. Ports to other platforms should be very easy and are underway.