In a recent post I quoted large amounts of material from the website of the U.S. Copyright office. I made the comment that I was not certain that that was not an infringement of copyright law.
I wrote the Copyright Office and was assured that information that is disseminated by government offices is not subject to copyright. Some information that appears on government sites is not original with the government. This material falls under "fair use", though, and is in the public domain. So, any material appearing on a .gov site may be copied freely.