Open source UMT code is now available at
https://github.com/tonygoacher/UMT_Open_Sourceand is covered by the zlib license.
It is written in Hi-Tech C Pro, which has a 30 day free evaluation. It is not complete yet and lacks zombie mode, respawn health and medic packs, but supports most ref. commands and clone.
Sorry for the 'C', but it's what I know....
It is written in a modular fashion, so it should be portable to just about anything. I'm going to be adding to this in the future, but if anyone wants anything adding just PM me.
Post to this thread if you want to know how it works.