Blubster is just another P2P-proggy:
The way Blubster works is to use basic peer-to-peer structured software without a central server, running a private UDP transport protocol: The MP2P Protocol. This system allows a user’s identity to remain private, which makes all the file-sharing process completely anonymous. Over 2 Years after its inception, MP2P has proven itself as a super-scalable and ultra-fast network.
The "M" in MP2P stands for Manolito, and the network is pretty similar to Fastrack (the technology used by KaZaA). If I'm correct, it's only used for MP3.

Here's a (small) description of the network protocol...