You've reversed it: "What next, you can only distribute Garageband-written songs through iTunes? You can only play Apple Guitar on stage at your gigs, and sell tickets through the App Store?"
It's not a question of only publishing if you use Apple's tools. It's if you use the (free) tool for profit you use their bookstore. Plenty of people publish (and sell records) through Apple using other tools now. Let's not get crazy about this.
I agree with +John Athayde
. There are other free and paid publishing tools out there. Use them if you don't want to be tied to Apple.+Joby Elliott
"why let it output anything? Why not just tie its export function straight into the Apple store?"
Maybe because they want to let teachers (and others) create their own material? This is a huge step forward for non-XCode iPad authoring. Some of you just have to dial it back a notch. Can you think of any other company giving away this kind of tool AND providing a direct link to the market if you want it?