Like Jeff said, Darkstar isn't really designed to be a streaming server, but there are other projects that do stream and are integrated with Darkstar. The MPK20 demo that Jeff mentioned is part of a larger project here at Sun to explore how distributed companies (like Sun) can use game environments to better communicate and collaborate. They have a robust VoIP bridge that they wrote, and they integrated this with Darkstar so that there's a VoiceManager that applications use, and which in turn uses Channels to do call management. It's pretty neat, and the goal is to make this service available so that anyone building on Darkstar can re-use these VoIP capabilities.
Is there somewhere I can read on this?