Crossfire is a multi-player graphical arcade and adventure game made for X. It has certain flavours from other games, especially Gauntlet and the rogue-like games (Nethack, Moria, Angband, and Ragnarok). Any number of players can move around in their own window, finding and using items and battling monsters. They can choose to cooperate or compete in the same world.
mcl is a MUD client running in a Virtual Console under Linux or using standard TTY routines under any other UNIX. Embedded Perl or Python offer very high tweakability. Other features include huge scrollback, a stable input line with the MUD prompt, Perl regexps for actions and substitutions.
ymusk stands for Yenzie's Mush Klient. It is a mush client written in Perl, and it is built around the Net::Telnet and Tk modules. It is meant to be a simple program which is easily customizable. Its features include logging, macro definition, speech filters, command history, and ANSI colors.
Mooix is a multiuser object-oriented dimension (a MOO) layered over top of your favorite Unix system. To the user, mooix looks much like any other MOO. To the programmer, mooix objects look like directories full of files: executable methods, properties, and links to other objects. MOOs have historically had poor support for such things as real programming languages, encrypted logins, multitasking, and editors. Mooix inherits all of these things from the Unix system it is based on. At the same time, it's not wedded too tightly to Unix (e.g., it implements its own permissions system that is much more suited to a MOO environment than the historical Unix system).
MudMagic Mud Client is a GTK/GNOME multi-platform MUD client. It provides aliases, triggers, multiple connections, plugins, MCCP, ZMP, MSP, tabbed sessions, ANSI color, and a game list that can be updated from mudmagic.com. It is configurable on a per-session basis. Plugins include an automapper, database, and note pad.
KildClient is a MUD client written with the GTK+ windowing toolkit. It supports many common features of other clients, such as triggers, gags, aliases, macros, timers, and much more. But its main feature is the built-in Perl interpreter. At any moment, the user can execute Perl statements and functions to do things much more powerful than simply sending text the the MUD. Perl statements can also be run, for example, as the action of a trigger, allowing you to do complex things.
Deliantra is an advancement of the crossfire multi-user RPG game. Unlike the original project, it focuses mainly on stability and playability, but also adds modern technology such as map scripting, Perl server extensions, asynchronous I/O, higher resolution graphics, and better client support.