I had some free time tonight so I finally got around to making the source to my Magnatune project open source. This is released under the Apache 2.0 license, so feel free to reuse within the terms of the license.
I also made the Magnatune API an official project, so feel free to start writing apps for it! I'd be very excited to see a BlackBerry client using this API, for example. I haven't quite finished writing up the documentation for the API at this point, but I'm working on it. If you have any questions, please reference the Magnatune application's source code or send me an email.
Note that I am not planning on releasing the source code to the API project at this point in time. It is very raw and not packaged in any sort of reusable format. Once those get fixed, I'll look into releasing it. Thanks for your understanding.