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.
Mason is a game system being developed by WorldForge. The primary focus for Mason is to enable players to build a persistent world in-game. Players will be able to manipulate items by creating new items from raw materials, attaching existing items together, or splitting items into component parts. Complicated structures such as houses can be designed on paper as a blueprint and then built with suitable building blocks and skills.
TinyMARE (Multi-user Adventure Roleplaying Epic) is a text-based MUD server completely rewritten for efficiency using TinyMUSH and TinyMUSE as a basis for its game engine. The server is designed for creating an extensive, novelistic role-playing atmosphere supporting real-time combat, day & night, seasons, and global weather. Using a telnet client, players can log on to explore a virtual world, find magical items, learn skills and techniques, and group together to surpass obstacles you create in your own epic adventure.
libtelnet is a small library for writing telnet protocol handlers in C. It uses a fully correct state machine model and full RFC 1143 (Q Method) option negotiation. It includes optional support for MUD-specific protocol extensions such as MCCP2 and ZMP. Several test programs are included, such as the very useful telnet-proxy utility.