I think you may be referring to US copyright law as opposed to European (which I thought was more lenient and should govern Boltzmann's work).
I think it's like sheet music that is in the public domain, they use the threat of legal action and strictly control access as a means of maintaining some revenues...
I think it's like sheet music that is in the public domain, they use the threat of legal action and strictly control access as a means of maintaining some revenues...