Habitat was originally written in 1985 by Chip Morningstar and Randall Farmer for Lucasfilm. After running a while on Quantum Link, a commercial network in the US, it was discontinued, and Fujitsu bought it. Fujitsu put a Japanese language interface to it, and has it running since 1990 on its commercial network NiftyServe, itself a lookalike of CompuServe. It has about 10,000 players, 1,000 of whom are regulars.
The world of Habitat is called Populopolis, its inhabitants are Avatars. Players can choose from a large collection of exchangable heads for their Avatar. The basic controls for movement and action are presented in the menu bar on the right. What is typed on the keyboard appears in a speech bubble above one's Avatar.
Like in text-based MUDs and in real-life, the more complex social interactions occure in the mind of the participants. Nevertheless, the visual and sound clues give additional opportunities for play, make it easier for beginners to orient themselves, - and a MUD-wedding is certainly something to behold.
There is a blossoming economy based on Tokens which are dispensed by ATMs (Automatic Token Machines) and accepted in Vendroids. Habitat emerged lotteries and politics, magic and and theatrical performances, like this one:
(See Chip Morningstar and Randall Farmer, "The Lessons of Lucasfilm's Habitat", in: Michael Benedikt (ed.), Cyberspace. First Steps, MIT Press 1991)