The difference is Apple has very deliberately created a closed garden for themselves and their consumers. I'm not happy with Apple's model, but at the same time I can't point to them and say they are hypocritical or self-destructive in their protectionism. They've done the work in-house to create the framework, the applications and the service...all the pieces necessary to have an integrated retail music experience. If they feel they need to protect that by excluding other services..that is highly self-consistent...even if its anti-competitive aspects of that policy end up causing them to defend themselves in a court of law at some point.
Canonical on the other hand...hasn't done the work necessary to build a closed platform like Apple has with iOS. Canonical's model relies heavily on the work being done by others in important pieces of their platform stack...in this particular case the upstream Banshee and GNOME developers. So when Canonical wants an inequitable high percentage of the revenue flowing through the banshee application...its both hypocritical and self-destructive. Heavily taxing growing revenue streams for upstream projects your platform is meant to rely on (because you don't have the engineering resources to build your own best of breed integrated applications) is eating your own seed corn for the sake of short term gain.
And let me stress the inequitablely high percentage of revenue part of that comment. The offer on the table was for Canonical to _take_ 75% of the revenue from the Amazon storefront they didn't build in an application they don't help develop. There is no mention if Canonical was also offering to _give_ 25% of the UIMS store revenue to banshee developers for producing an application that Canonical could use instead of Canonical expensing the manpower to build their own app.
If Canonical wants to mimic the closed garden revenue stream control that Apple has over iOS,then Canonical needs to go back to square one and build a closed garden that they can control instead of trying to pound an open ecosystem model into a closed garden model...it's a round peg/square hole situation.