Copyright, Public Domain, and Licensing are three ways to evaluate the right to copy something.
Copyrighted materials are protected by law from copying, though protections vary according to circumstance. "Limited" amounts of protected materials can often be legally copied.
Public Domain materials are not protected by copyright.
Licensed materials are protected by contract rather than copyright law, and the rules of copying are determined by the contract. In the case of the Thrift Library, many of its databases contain materials which are licensed for copying.
Even after you've fully educated yourself about fair use (the information on our site is just a start), it can be difficult to remember all the relevant issues when you're looking at a potential use you'd like to make. We've developed one tool that may assist you in your thought process. The Office for Information Technology Policy of the American Library Association also steps you through the process with a similar interactive tool.