Dark Ages II: Engel
   Medieval Windows game in which three thieves must solve the mystery that unravels when they are betrayed by their guild.
   http://dk-software.com/

DimensioneX Multiplayer Adventure Development Kit
   Offers a freeware Java software capable of building and running multiplayer adventure games, playable with any browser. Several multiplayer games are available for free as a demo.
   http://www.dimensionex.net/en/

Dungeon Game
   3D dungeon crawler for Windows or Linux.
   http://tempusmud.com/~jwatson/sdl-dg/

Exult
   Version of Ultima VII for Unix, Windows, Mac, BeOS.
   http://exult.sourceforge.net/

Faldon
   Online role playing game for Windows with equipment, items, magic, skills, levels, experience, and a real-time battle system.
   http://www.illusorystudios.com/faldon/

IRE
   User-editable clone of Ultima 6 for DOS, Windows, BeOS, or Linux. (Open Source, BSD)
   http://ire.sourceforge.net/

K2W RPG
   A collection of open source client, server, and editor you can use to build and run your own online RPG.
   http://www.k2wrpg.org/

Lost Hero
   A classic-style Java-based game, with information and download.
   http://losthero.sourceforge.net/

Progress Quest
   Players build their character from a ninety-pound level one teenager, to a warrior, well able to snuff out the lives of a barnload of bugbears without need of so much as a lunch break. (Windows)
   http://www.progressquest.com/

Realms of Kaos
   Features message boards, rules, chats, downloads and FAQs.
   http://realmsofkaos.com/

Umbra
   Free humanity in a randomly-generated world. (Requires Python)
   http://kuoi.asui.uidaho.edu/~kamikaze/Umbra/

Wheel Of Time - Light And Shadow
   An online virtual community in Java based on Robert Jordan's Wheel of Time books. [Open Source, GPL]
   http://wotlas.sourceforge.net

Zelda Classic
   Replica for Windows of NES version of The Legend of Zelda. Includes development notes, download, enemy list, walkthroughs, and FAQ.
   http://www.zeldaclassic.com