They are an ARM licensee. ARM was acquired by NVIDIA. If there's bad blood between NVIDIA and Apple, all the more reason for Apple to drop ARM and go with a custom, Apple-designed ISA.
Apple has a lifetime license for ARM. There is nothing Nvidia can do to Apple on this front or any other.
But more than that, Nvidia needs Apple. Apple selling ARM macs to developers means that all developer tool chains are being updated to support ARM. This is vital to Nvidia’s plans of ARM server chips. It would never have been a reality without the M1 or something like it.
ARM is a joint-venture between Apple and Acorn, each had 43% of the capital back in 1996. Apple has a lifetime architecture license, they couldn't care less about who own ARM...
Not sure Apple would ever go completely custom, their MO when they need a component is to try to find something existing first (webkit, llvm) and adapt it. If there was bad blood they’d sooner adopt RISCV.
