Essentially, you post iTunes Music Store links on your website and collect a 5% commission. I haven’t ran through all of the details yet, but I’m kind of fascinated. Since Apple themselves can’t be making much more then 5% per song, it’s entirely possible that an affiliate could set up a front end to Apple’s store and actually end up making more money off of it then Apple is. Admittedly, the total amount of money involved would be fairly small, and I doubt Apple is giving the affiliates a cut of the iPod sales (which is where Apple really makes their money on music), but it’s still an interesting concept. At the very least, blog-based music reviews and experimental music recommendation systems are going to get a boost.
Of course, knowing Apple, there’s something unpleasant hidden in the terms of the affiliate program. Either that, or they’ll change the program mid-stream and leave people screwed. Apple occasionally rivals Microsoft for the “world’s worst business partner” title.