When Apple announced that it was no longer going to include Digital Rights Management on songs downloaded from the iTunes store, it all looked rosy—but there is a hidden catch. The AAC (.m4a) files still have your iTunes account id embedded in them so it can still be determined who bought them. That is unless you can find a way to edit the file to remove this information. Mediamonkey says it can edit AAC tags but I don’t know if it includes this one.