[threeseed]

a) For almost all developers it's 15%.

b) It's under scrutiny but the legal consensus being formed is that Apple simply needs to allow links to alternate payment systems. It doesn't need to allow sideloading or offer alternate app stores.

c) Some countries are looking at forcing Apple to offer a "choose your phone/mail/calendar app" screen on initial phone purchase which does have precedent and looks far more likely.

[klelatti]

We’re talking about the impact on Apple here and the large majority of their income will come from developers that are in the 30% tier.

Whether it’s another App Store or a link either way will affect Apple’s take through the App Store.