MUDs first appeared in 1978, and their popularity escalated in the USA during the 1980s, when (relatively speaking) cheap, at-home personal computers with 300 to 2400 baud modems enabled role players to log into multi-line BBSes. Roguelike games were also becoming popular at that time.
In Europe at around the same time, MUD development was centered around academic networks, particularly at the University of Essex where it was played by many people, both internal and external to the University.
The MUD scene is still very much alive on the Internet, and can be accessed via standard telnet clients. Specialized MUD clients exist that give a more pleasant user experience.
The original MUDs drew their inspiration from paper-and-pencil based games such as Dungeons & Dragons; (hence their name), and the computer game Colossal Cave Adventure. The first MUD was probably created and written by Roy Trubshaw and Richard Bartle at Essex University in the UK[1] although the book "Dungeon Master" by William Dear, and some other sources suggest there were earlier MUD games that the Essex authors never knew about.
A version of this first MUD is still running at www.british-legends.com and a version of its descendant MUD2 runs at www.mud2.com. The first popular MUD was AberMUD written by Alan Cox, also known as Anarchy, named after the University of Wales Aberystwyth. Over time variants have diversified into other models while retaining the textual format. For example, some variants are called MUCKs, MUSHs, LPMUDs, and MOOs.
A MUSH is often said to mean multi-player shared hallucination. MUSHes descend from the program TinyMUD. MUSHes date back to the early 1990s. They are more directly concerned with role-playing (acting) than MUDs, dispensing with the experience systems. Instead, players focus on creating their character's life as accurately as possible. Members of the MUSH family include PernMUSH, PennMUSH, TinyMUSH, TinyMUSE and TinyMUX.
A MUCK, which is an acronym of multi-user chat kingdom, is similar to a MUSH in that the emphasis is on player interaction, rather than action and questing. MUCKs and MUSHes differ from IRC as a chat medium in that they provide a world, character descriptions etc in order to flesh out role-playing chat.
A MUVE is a fairly recent term which is the acronym of multi-user virtual environment. Its goal is to simply have a less narrow or ambiguous acronym for the genre.
Other variants emphasize building by providing players with a powerful programming language (as in MOOs) to make their own objects and rooms, or function as elaborate chat systems with no fantasy trappings.
When referring to MUDs, MUCKs, MUSHes etc. all alike, the term MU* is often used.
A lesser known variant is the talker, typically based on ew-too, summink, sensi-summink, playground, and plenty of other code bases. The talker is essentially a MUD, with most of the complex bits of code stripped away, leaving just the communication level commands -- hence the name talker. People who use these tend to be called spods.
The spod tends to be something of a long term fanatic. Where many mudders may move on after a year or two, people who use talkers typically have been doing so for a decade or more. Talkers are signifigantly easier to run than an average MUD, since they don't incorporate very much artificial intelligence, and they are usually much more user friendly, since there is not often much fighting as a focus. In other words, whole families of husbands, wives, children, and siblings have been known to spod in certain circles.
They also use very little network traffic, and use simple protocols, making them ideal for setting up quietly at work. Talker applications predate MUDs by many years, although some of the early ones were used to play Dungeons & Dragons; over computer networks.
When speaking of Medievia, it should be mentioned there has been quite a bit of controversy about its origins. See KaVir's Medievia page for information.
The Cold Project A group of programmers involved in developing in ColdC. ColdC is an object-oriented database language designed for setting up persistent online servers, such as MUDs. http://www.cold.org/
FTP.GAME.ORG Mud Archive A directory of MUD server sources and other related files available for FTP, organized by server type. http://www.game.org/ftpsite/
Momoko An open source, modular, extensible platform for building multi-user environment. Momoko transparantly distributes objects over multiple servers and supports several scripting languages. Written in Java. http://momoko.sourceforge.net/
16K MUD Competition Results Results of a competition to write the best possible MUD server in under 16 kilobytes. http://www.andreasen.org/16k.shtml
DUMB MUD The 'Diabolically Uncrashable MUD Builder' project aims to provide a server that is first and foremost stable and reliable. The DUMB language is a dialect of Lisp. http://jlmud.sourceforge.net/
The Grendel Project A MUD server for Win32 written in Delphi 5. Features include multi-threaded design, copy-over procedure and IPv6 support. http://www.grendelproject.nl/
Muq Ambitious distributed MUD server with a long list of features. One of the main aims of the project is to construct non-proprietary online communities based on free software. http://www.muq.org/
The AIME Project An open-source MUD engine, designed to provide as much flexibility as possible to the designer creating the online world. http://aime.sourceforge.net
MUD eXtension Protocol (MXP) An open specification for enhancing the communication between MUD servers and clients. It is loosely based on the HTML and XML standards. http://zuggsoft.com/zmud/mxp.htm
Valhalla Mud Engine MUD engine by the original writers of the DIKU MUD server. Unlike DIKU, VME is available under a business license that allows commercial exploitation. http://www.valhalla.com/vmeinf/index1.html
New MUD Code-bases Catalog of new and original MUD servers for different platforms and programming languages. Includes short descriptions and links to the project web pages and their authors. http://www.andreasen.org/newmud/
Kanga.nu MUD Server FTP Archive Repository of MUD servers containing many old servers of historical interest, as well as new ones. ftp://ftp.kanga.nu/pub/MUD/Servers/
Majik 3D A project to create a 3D online role-playing environment set in a medieval fantasy world. The server uses proprietary technologies provided by Taika Technologies. http://www.majik3d.org/
Mud Server Developer's Page Information and links related to mud server development. Aims to maintain a comprehensive list of mud ports for Windows. http://pw1.netcom.com/~jlsysinc/index.html
CGMUD Graphical MUD system ported from AmigaMUD. Has a graphical MUD client written in Java and an efficient server written in C. CGMUD is not derived from any other MUD and has no licensing restrictions. http://www.graysage.com/cg/MUD/CGMud/index.html
CoolMUD Server CoolMUD is an object-oriented, disk-based MUD server originally written by the creator of MOO. It has support for distributed processing. This version features some bug fixes in the server and improved in-database code. http://www.digitalkingdom.org/~rlpowell/coolmud/index.html
KoalaMUD Koala is a highly-distributed IP6/IP4 MUD server. It allows for very large game worlds to be distributed between multiple machines in a manner transparent to players. http://koalamud.sourceforge.net/index.php3