Though the existing version of Age of Dragons (now renamed to Gates of Krynn) runs using CoffeeMUD, the classic CircleMUD game is still online. Though it does not receive a lot of attention from the main development crew who are dedicated to the CoffeeMUD version, the classic game is still a very fun, well done game that has a lot to offer both past players and new ones.
The classic game is quite akin to the Advanced Dungeons and Dragons tabletop game, both in terms of challenge and many of the mechanics that are in effect. It offers a number of races and classes, as well as an introduction system a spell memorization system instead of mana, custom and detailed character descriptions instead of just a name or a gender and race, and many zones that are very well done both mechanically and descriptively.
If you're an old player, and would like to help in continuing developmental progress or otherwise offering leadership to the classic game, please contact Gicker via email.