It makes the empeg act like a RioReceiver. It is based on an open source version of the Rio Receiver client software.

The official Rio Receiver client doesn't support streaming shoutcast. The one this hack is based on does. Aside from streaming shoutcast, it also has the ability to stream MP3s from a server. That is why you would need the Rio Receiver Server software.

I would assume that once you install this hack, the tunes on your empeg's hard drive are no longer accessible.