This code is distributed under the 3030MUX Artistic License, a modified Artistic License, which you should find in a file 'LICENSE' accompanying the actual source code. The changes to the Artistic License are minimal: sections 3.b, 3.c, 4.b and 7 are scrapped, and the rest of the sections were renumbered to fill the gaps. No other changes were made. The net result of these changes is that if you want to host a game with a modified version of this source, you HAVE TO make that source available. Either by publically putting it up a website, or by sending it back to the original authors (a SourceForge patch submission will do.) You do not, however, have to wait for the authors to incorporate the changes before you use them; making them available is enough.
The rest of the Artistic License restrictions are the same: You cannot charge money for this source, though you can charge money for supporting this source. MUX 'softcode' that you use in a game is considered part of the configuration/scripting of the MUX, and does not fall under the 3030MUX Artistic License: you can do anything you like with it, including selling it.
The original authors of the code retain their copyright. The source is not yours. You are given permission to use it. Actual authors are listed in the files themselves. When attribution in the 'src/' directory is missing, assuem David Passmore. When attribution in src/hcode or any other directory is missing, assume Markus Stenberg. If you see code of your own unattributed, please let us know.