Linden Lab released their capabilities server under an MIT license yesterday. It is written in Python and available as part of the mulib package (trac view here) which was released as Open Source earlier.
The capabilities server is one of the core modules needed for the Second Life Grid to run and will play a big part in the interconnectivity protocol which the AWG is working on. If you want to know more about Capabilities please have a look at my summary.
What’s missing unfortunately seems to be a test (I would like a doctest) explaining how it works. Thus I will try to figure it out soon and might report back.