Public Domain = Anyone can use it for any purpose; it's free to use without restriction.
Royalty Free = Someone else owns it, so you can't own it; but, you can borrow it.
(Public domain: free within the U.S.)
Digital Public Library of America
The Library of Congress
Rare Book Room (Public domain: free within the U.S.)
University of Pennsylvania
Each item is individually labeled, so make sure you read the small print!)
World Digital Library
Creative Commons Licenses =
Provides an excellent summary
of access and use definitions and policies.
last updated 5/19/2016 by Arlen Kimmelman, CRHS Library