As for the "terms of the deal" - that is only relevant if nobody bothers to download these images now. The images are all so old that the originals are out of copyright, and as far as I can see, the British Library have tagged them all "no known copyright restrictions", as Microsoft, who did the scanning, donated them to the public domain.

So these complaints are meaningless: Have a concern about the hosting? Mirror the images. As I'm sure various people will.

Even if Flickr were to shut down tomorrow, British Library still have them, and likely Microsoft too. And the books they are from still exists. It is the British Librarys job to ensure the preservation of the source material -, and they can provide them to other parties.

IMO the U.S. Library of Congress does it right. They do actually have a Flickr page, for people who prefer that interface: http://www.flickr.com/photos/library_of_congress/sets/

But there is also the canonical digital archive at: http://www.loc.gov/pictures/