The digital scans are public domain [1] though I think you have to do a little digging on NASA.gov for the raw TIFF data. It's the
remastered images made by Andy Saunders that aren't in the public domain. Anyone is free to make their own remastered versions and release those into the public domain (or make a competing book/print service)
[1] https://www.flickr.com/photos/projectapolloarchive/albums