Website: http://britishart.yale.edu/collections/search
Conditions:
Thousands of images of works in the Center’s collection believed to be in the public domain are available for free through the Center’s online collection catalogue. Under Yale University’s Open Access Policy, anyone may use the Center’s open access material without further application, authorization, or fees due to the Center or to Yale.
Source: http://britishart.yale.edu/collections/using-collections/image-use