NIST, the National Institute of Standards and Technology publishes reference libraries of hundred of thousand of compounds. I would like to use these in my computer for GC data, however it looks like they have to be purchased from the instrument distributor, in my case Thermo. My question is more about politics, being NIST a U.S. Government agency I was under the impression that every work of a government employee is in public domain, therefore free. Why are these libraries in particular not free to download?