The US government provides a number of closed-source software packages to the public for free. Some packages are explicitly listed as "public domain"; other packages list a specific agency as the copyright holder. Packages might be written by US government staff, contractors, or both.
These programs frequently contain EULA language forbidding decompilation or reverse engineering. Since the software is given away for free by the government (i.e. the US government does not profit from the software it releases), the reasoning for that EULA language is not entirely clear to me, and I wonder about its validity.
Is is legal to decompile or otherwise reverse engineer free, publicly available software from the US government? Has a case ever been brought against someone for reverse engineering such software?