MCL is a MUD Client for Unix. Under Linux, it uses the Virtual Console interfaces to access the screen at a high speed, but it can also run in a TTY mode, allowing it to run under any other UNIX and in an xterm. Embedded language support (currently Python and Perl) allows high tweakability.
Xpertmud is an extensible perl and python scriptable MUD client. It is based on Qt and KDE. There's a native Linux/KDE version as well as a native Windows/Win32 build. This enables you to use the same script on your Linux box at home and on your Windows box at work...
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. You can at any moment 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.
PMC is a text based mudclient written in Perl 5.
It utilizes GNU readline, supports SSL, local editing support through MCP (MudClientProtocol), full telnet negotiation support and of course ANSI support if your terminal supports it.
Unlike other mudclients with input line editors/history, it also supports the telnet character mode, which enables it to use e.g. fullscreen applications within a mud (like the xeditor found on some LP Muds).
TinTin++, aka tt++, is a free MUD client for Mac OS X, Linux, and Windows. The Windows port named WinTin++ (using the PuTTY terminal) is available for those who do not use Cygwin (A Linux/Unix emulator for Windows) and runs on Windows Xp, Windows Vista, and Windows 7. Besides MUDs, TinTin++ also works well with MUSH, Rogue, BBS, and Linux servers.