I believe the problem lies in the wording of ‘exact’. Without a direct comparison to the source material ‘exact’ could be challenged. There’s also the problem o

I believe the problem lies in the wording of ‘exact’. Without a direct comparison to the source material ‘exact’ could be challenged. There’s also the problem of exact dating of a piece of art as being pre-1923. With a reproduction in a published book you have a publishing date in the colophon that logically must be the same year or later than the reproduction of the artwork inside. Without that you’re relying on the artist’s date of death or supporting material such as an original bill of sale to make the distinction. Basically, the problem is that when you’re releasing a derivative work with CC0 you need to be 100% sure that your original licensing is correct. We’re probably being overly-cautious, but luckily the imprint style allows us to be. (The A4 licence comes from their T&Cs PDF: “Images of the Van Gogh Museum collection up to and including A4 size in TIF format may be downloaded and distributed for non-commercial use”.)