Paris Musées, a group of 14 public museums in Paris, has made a splash by releasing high-res digital images for over 100,000 artworks through a new online portal. All the works were released to the public domain (CC0, or “No Rights Reserved”), and they include 62,599 historic photos by some of the most famous French photographers such as Eugene Atget.
Where on the site did you find that statement? Under the copyright section, it states (emphasis added):
CREDITS
All materials published on the Website parismuseescollections.paris.fr, including texts, photographs, graphics, and icons are the property of Établissement Public Paris Musées, the City of Paris, or of parties from whom right of use has been obtained. Consequently, any representation or reproduction for other than personal use that may be made of them without the consent of the authors or their assignees is unlawful.
I found that after a search (in French), depending upon what you select, the restrictions on use (and availability for download of high res images) varies.
Luckily I think the copyright info is covering their museum page info and graphics etc. Another great museum site to spend hours perusing, thanks @lightner!