SCOTUS has ruled[0] that use (including implementation) of APIs is fair use, and does not constitute copyright infringement if the author of those APIs wishes to place restrictions on them.
A developer writing an app for iOS can use the APIs provided by Apple without agreeing to license them.
(Granted, you can't get your app into the App Store and onto iPhones/iPads without agreeing to whatever Apple wants you to agree to. Which... is part of the problem.)
Probably not that much considering the past, present and future totals of a 30% cut across all developers lmao. We're talking about a LOT of money here. There's a reason Apple is a "trillion dollar company" and it's not because they're putting in anything even close to as much as they take out.
If it were possible to run unsigned code on the average iDevice (and Apple's framework/drivers disabled for unsigned code) then this would have already been done, a long time ago.
If that one person does it and lets everyone use it, will they do it for free or should they charge for it, perhaps as a percentage of revenue of the developers and applications who use the code?
“Not that much” as in a billion dollars? Ten billion dollars? 100 billion dollars?
Nobody has been able to build a new browser engine in 25 years. So what would be the dollar estimate of a similarly complex UI framework along with high quality device drivers, development tools, services frameworks like iCloud, etc.?
A developer writing an app for iOS can use the APIs provided by Apple without agreeing to license them.
(Granted, you can't get your app into the App Store and onto iPhones/iPads without agreeing to whatever Apple wants you to agree to. Which... is part of the problem.)
[0] https://en.wikipedia.org/wiki/Google_LLC_v._Oracle_America,_....