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.
