> technically one can claim recompression is transformative No, because transformative applies to uses of the work, not the work itself. A recompressed image h

> technically one can claim recompression is transformative No, because transformative applies to uses of the work, not the work itself. A recompressed image has the same uses as the original image so there's absolutely no scope for considering it to be transformative. As far as attaching licenses to public domain works goes, you can do what you like. There are no restrictions. However, you can't claim to have an exclusive license, and you certainly can't claim to own any copyright in the work, because none exists.