MUSH
A MUSH (Multi-User Shared Habitat, or Hallucination) is a text-based online social medium to which multiple users are connected at the same time. MUSH are often used for online social intercourse and role-playing games, although the first forms of MUSH do not appear to be coded specifically to implement gaming activity. One of the earliest forms of MUSH that existed are tinyMUSH and tinyTIM. MUSH has forked over the years and there are now different varieties, such as PennMUSH, with different features. The source code for MUSH is open source and available from its current maintainers.
The differences between MUSH and prior MU* languages, such as MUD and MUCK, are the inclusion of many visible flags which, when appended to a user name, signify special properties that apply to that user account. One example that is often given is that if a character is set as ENTER_OK, they can be entered just as any virtual room within the text-based world of MUSH; a flexibility that differentiates it from earlier MU* where rooms and entrances, objects and players were all coded to operate as non-interchangable states of design.
The programming language for MUSH is said to have been designed by Larry Foard, and this report seems reliable.
Roleplay on MUSHes
Traditionally, roleplay consists of a series of 'poses'. Each character makes a 'pose' - that is, writes a roughly paragraph-length description of speech actions, etc. which the character performs. Special commands allow players to print OOC messages, distinguished by a prefixed tag from IC action. This medium borrows traits from both improvisational stage acting and writing.
See Also
External Links
MUSH Warehouse (http://www.moosh.net/mush/mushlist.shtml) List of MU*s