It's a streaming mp3 server. It's written in Python, so you gotta have that installed, but it serves up streaming mp3s through a web interface. You can set access restrictions based on username:password combos as well as domain/ip restrictions (least, that's what it looks like from the config file). Configuration is cake, too, which is a nice plus.
most peeps likely won't care, but for myself it'll be nice to have all my music in one place again.