It’s generally accepted that file formats aren’t protected IP, so you can write a compatible reader or writer and be in the clear as long as you reused no code from the original reader/writer. The specification may have licence terms that restrict who you can share the spec with, but you don’t necessarily need the official spec to come up with a compatible implementation. Plenty of file formats have been reverse engineered over the years even when the original didn’t have a written spec.
It’s generally accepted that file formats aren’t protected IP, so you can write a compatible reader or writer and be in the clear as long as you reused no code from the original reader/writer. The specification may have licence terms that restrict who you can share the spec with, but you don’t necessarily need the official spec to come up with a compatible implementation. Plenty of file formats have been reverse engineered over the years even when the original didn’t have a written spec.