It's Apple's phone, they can do what they want.
The apple webpage says
> Why buy iPhone anywhere else?
> When it comes to purchasing a new iPhone, there’s no better place to buy than Apple. For all your questions about payment options and getting your new iPhone set up, we have the answers you need.
If you don't agree, don't sign it.
I understand a one time fee ($99 or something) for hosting the app and allowing downloads, but why does Apple get an ongoing 30% cut?
And of course the absolutely massive SDK that makes it easy to build all these apps natively without rolling your own computer vision framework or audio processing engine.