I have bought over 900 songs from the iTunes Music Store. When I want to listen to this music on my TiVo, I need to convert it to the mp3 file format. Using iTunes the only way to convert protected AAC files to mp3 is to burn the tracks to an audio CD, and then rip the CD.
Also, this process doesn't work well if you don't convert a single album. You can burn tracks from different albums onto a single CD. But when you rip the tracks, all of the track numbers and album names are incorrect.
JHymn is a java application that allows you to convert the music that you purchase from the iTunes Music Store, into a unprotected format. In addition to converting it to a unprotected format, you can also have the audio file converted to mp3.
It looks like JHymn connects to the iTunes Music Store, and registers itself as a computer that has access to your music. Since it has registered itself with the iTunes Music Store, it gets the playback key to decrypt the music. Then it converts the music to WAV format, and then converts the WAV files to mp3.