(Formerly Basternae 3)
A modern multiplatform multi-user dungeon engine written in C# and .NET with a full toolset.
By multiplatform, I mean that the compiled MUD runs on Windows and Linux, but I do not recommend compiling using any tool other than Visual Studio. There are subtle differences in the output binaries that can cause trouble (i.e. terminal glitches) if you build on Linux using xbuild/gmcs. This has not been tested on OSX, but would probably work about the same as on Linux.
In addition, some of the editing tools do not work fully under Mono, due to this RTF colored text rendering bug in Mono core:
https://bugzilla.novell.com/show_bug.cgi?id=593951
The engine itself uses C# .NET 2.0. There are four clients, one using C# and Silverlight, one using WPF and C# .NET 3.5, one using C++ and wxWidgets, and one using C++ and SDL. None of them are fully feature-complete, but the WPF client is in the best shape of the three (and the Silverlight client worst). There is still work to be done on the ANSI color parsing in all of them.
Documentation is in the /docs folder. Starting with the README.md file in that folder is a good first step.
ModernMUD was in production use for Basternae 3 MUD, but Basternae has been discontinued.
For a less-modern multiplatform MUD engine written in C, see Magma here:
https://github.com/Xangis/magma
For a tool to convert MUD zones in other formats (Magma, Basternae 2) to ModernMUD format: