I've asked permission from @datdenkikniet and they have agreed to relicense the code to stm32h7xx-hal under 0BSD. I have added the relevant acknowledgement headers in the appropriate files as requested by them as well. i believe there are more changes that need to be made before merging, but hopefully this means that this PR can get merged after that @adamgreig @richardeoin

Confirmed! The bits of code reused in this PR are relicensed under 0BSD (new bits, too, so long as I've authored them. I can't speak for authors other than myself, but AFAIK we're not touching any of that here). We discussed and this seemed like a reasonable approach :)

PR is ready for review