I found this interpretation of the law in the UK with regard to "fair use" and thought it might be of interest.
FAIR USE - Fair use is a limitation on the exclusive rights of the copyright owner; in other words, it allows reasonable public access to copyrighted works.
The idea is an important part of the English common-law tradition.
Why does FAIR USE exist?
FAIR USE allows people to use images and written works without compensating the original writer/creator, as long as they act in good faith and do not profit from reproducing the work. Education, parody, criticism, news reporting, etc are all examples of fair use.
The idea of FAIR USE has guided the use of reproductions of works for years. In most cases, the lack of commercial gain is necessary for a claim of fair use. If you are a non-profit website designed for educational purposes, you are in the perfect position to claim FAIR USE of images which are already in the PUBLIC DOMAIN.
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For a long time, the FAIR USE doctrine occupied a grey area of law, usually decided on a case-by-case basis. Typically, if someone were profiting from another person's work which was not in the PUBLIC DOMAIN, it was not considered fair use. Museums typically did not sue non-profit websites which reproduced images for educational purposes. If they had, the court would have forced them to prove a substantial loss of profit from the use. Understandably, such proof would not exist and the court would not look favorably upon such a vindictive case, particularly since the images were already in the public domain.
Regards Allan.