The Getty has made 1000s of images of artwork that is in the public domain available online. Like Philosophy Presenting the Seven Liberal Arts to Boethius (c. 1460-1470CE) by the “Coëtivy Master”*:
Like other museums that share portions of their collection online, this make an experience of the Getty’s collections available for people around the world, who cannot actually visit the Getty. While the works of art themselves are in the public domain, the Getty might claim copyright over the scans/photos of the art. Instead, they have taken the step of making clear that this images are available for the public to use and adapt as we see fit.
The Getty makes available, without charge, all available digital images to which the Getty holds the rights or that are in the public domain to be used for any purpose. No permission is required. – The Getty “Open Content Program”
I don’t know if letting me print 300dpi images of classic art will hurt The Getty’s bottom line due to reduced gift shop sales of postcards (not from me, the gift shops never have the pieces I want). Hopefully, The Getty’s program will inspire other museums to consider following suit.
*The results of a search for “science” were a bit disappointing, but I suspect that this is mainly due to the age of many of the works. Using a historically relevant term, like “philosophy” was much more productive.
**Hat tip to Hannah Williams.