There is plenty of legal case law on this ranging from BSD to various proprietary licenses. You would not win on this. This is why Compaq had to do a clean ro

There is plenty of legal case law on this ranging from BSD to various proprietary licenses. You would not win on this. This is why Compaq had to do a clean room implementation of the BIOS back in the 80s -- the law of doing it otherwise was already clear back then.