It's (mainly) bullshitIt can't be used in ways suggesting an endorsement by the subjects, but as a work of the US federal government, the law specifically says they can't claim copyright or prevent derivative works.
www.usa.gov/copyright.shtml
(www.usa.gov/copyright.shtml
the wub - guide onion for the blind,
Tue 3 May 2011, 13:01,
archived)