From what I've seen, one of the requirements of a competing App Marketplace on iOS is that they allow any developer to submit apps to them—I'm unclear on whethe

From what I've seen, one of the requirements of a competing App Marketplace on iOS is that they allow any developer to submit apps to them—I'm unclear on whether they can restrict by category (eg, only allow games), but AIUI they can't just restrict their own marketplace to selling the apps they themselves publish. This is a very interesting requirement, and will definitely at least make companies like Epic, Valve, and Facebook pause and think before deciding whether they actually want to be running an App Marketplace.