IANAL but on a technical level I'd say it's clean room and not subject to the original copyright for at least 2 reasons: the LLM for sure hasn't seen init code for this platform before, and there is no leak on the internet. It hallucinated register semantics often, suggesting it hasn't seen the original code. Also, coreboot code looks and, to some extent, works differently than the vendor reference code that I have seen for other platforms, making it not subject to any copyright claims. Lastly no copyright claim can be made on LLM generated works, but given the non-negligible human effort put into this, I'm not sure what the upshot is here. Still non copyrightable does not mean it's not free, it's something like public domain.