There are three ways you can customise SlashMUD:
The world files (armours, armourtypes, clans, classes, moods, monsters, moods, races, socials, weapons, weapontypes and zones) are plain text, allowing you to customise the world with your favourite text editor.
The SlashMUD Plugin API provides an interface to the server for Plugin Attachments, Monsters, Races, Rooms, Skills, Things and Weapons. Plugins can be written in C or C++ using nothing more than a text editor and the Developer Tools that come with Mac OS X. The source code can be downloaded from the SourceForge SlashMUD project pages.
Because SlashMUD is Open Source software, you can play around with the source code. The SlashMUD server is written in ISO C using BBEdit and the Mac OS X Developer Tools (autoconf, autoheader, bison, flex, gcc, gperf and make).