Because now we have a really good software, we want it to be on a really good legal grounds. Nothin'is shaky here. Mint your token at happyminter app, it's in limbo - I'd check myself that it comes from a museum with 100% free Terms of Use, we'd not accept a new token with less than 'open access' which means Public Domain on the artwork, yes, but from a museum that doesn't have restrictions on the use of the downloaded image. Artwork is PD, but its image is not - that's mostly the case with 'bad' museums.