With the release of iTunes 7 Apple once again changed the authentication mechanism by which non-iTunes clients can connect to iTunes Music Shares. There is a small community of hackeres working to reverse engineer the new encryption, which is significantly more complex than iTunes 6's.
The focal point of the project is Justin Stanley's Save OurTunes project, which has raised several thousand USD to reward the person who cracks iTunes 7's new Client-DAAP-Validation encryption.