Comment by bitwize

> Or similarly, a hypothetical claim by Intel that a compiler such as LLVM is derivative work of the x86 ISA.

Intel has been lenient toward compiler implementers, but their stance is that emulation of x86 instructions still under patent (e.g., later SSE, AVX512) is infringing if not done under a license agreement. This has had negative implications for, for example, Microsoft's x86 emulation on ARM Windows devices.

(I'm guessing Apple probably did the right thing and ponied up the license fees.)