Apparently, works prepared by employees of the U.S. government are in the public domain, including website content.
According to the Commerce, Energy, NASA, Defense Information Managers Group:
In accordance with 17 USC §10571, works prepared by government employees as part of their official duties are not subject to copyright protection in the U.S. (See FAQ Sections 3.1.1 and 3.1.2). This applies to government employee prepared works posted to government Web sites and to the government website itself if government employees as part of their official duties prepare it.There is a catch. Not all content on government websites is created and/or prepared by government employees. Government websites can contain:
- Copyrighted text that the government entity is licensing from the copyright owner
- Logos, images, graphics created by a contractor (which are subject to copyright)
- Syndicated news briefs that come from a website that may or may not copyright their content
Some sites, like the National Institute of Health's MedLine Plus, have pages that make a distinction between copyrighted and public domain content on various pages. Others provide attribution on pages that feature copyright content.
I recommend checking with the government entity if you are going to use a significant amount of content. When I did they were thrilled to share their content.