Buyasta is also (yet another) MUD engine written in Python. The primary goal of this project is to provide a simple-to-use framework for constructing MUDs. Consequently, the Core library implements the bare functionality required for every multi-user environment (i.e. an engine, base objects, rooms, etc). Why such minimalism? In my opinion, engineering something as complex as a virtual world should be a bottom up process. More often than not, implementors end up striping away most of a MUD distribution before proceeding on with actual development. With Buyasta Core, you won't have to. Just build on top of it.
Since Buyasta is more of a library, a secondary goal (not secondary in priority though!) is to produce thorough API documentation and tutorials. We strive to make documentation a first class citizen of this project!
. . . Of course, I wouldn't be working on this if I didn't have my own delusions of grandeur - and my extensions to the core are also included in the source package.