Pretty sure Apple has a permanent ARM license. They'll watch what happens with Nvidia, but it doesn't really affect them because, as you say, all the secret sauce is in-house.
Does that give them control over the direction of the ISA - suspect not. Don't think it's really the case then that they're unaffected by the Nvidia takeover.
Most companies buy the ARM CPU RTL or an existing hardened core for their chip.
Large companies like Apple have an architectural license and implement the entire instruction set on their own.
I worked for a couple of companies with ARM architectural licenses and there was a large ARM compliance suite of tests that had to be run and pass before you could claim that you made an ARM instruction set compatible CPU.
I have heard that Apple does not claim ARM compatibility and doesn't run the compliance suite which allows them a few shortcuts and other optimizations. Apple only cares about running Mac OS and iOS on their hardware so if they were incompatible with Linux/ARM or Windows/ARM they wouldn't really care.
I haven't been able to verify this. Linux/ARM seems to be running okay so far on the new Apple M1 chips.
I don't know if Apple would be affected much if Nvidia buys ARM. Their architecture license to implement from scracth is probably forever but maybe not
Interesting - especially that Apple gets some latitude on compliance.
Still leaves Apple open to potential Nvidia's changes to the ISA's direction (and the ISA won't stand still). I assume a full fork of the ISA isn't on the cards even for Apple.
I suspect Apple's rights might be spelled out more in the sales contract to SoftBank than in a separate license agreement. Acorn created the ARM processor, but Apple is a cofounder of ARM Holdings (Acorn, Apple, and VLSI Technogology).