I don’t know what Muff is talking about. What you just described is definitely do-able. Hell, you can obtain a copy of an LvMI work, make copies of it, and sell them if you wanted, right now. And you don’t even have to pay for the original work…you could download it for free. Everything produced by LvMI is released under CC BY 3.0 license (which is basically as close to no copyright as you can get, aside from CC0, and the only reason they don’t use that is because “efficacy looks doubtful to [Kinsella], and it’s still embryonic as far as [he] can tell”). Even the mises.org website is CCBY3.0.
So yes, you could easily go to the resources page for, say, Lesons for the Young Economist, download it, send it to a printer, bind it into book form, and start selling it. Or you could download the epub and offer it for sale on your own website.
And again, as I said, Rothbard talked about using contracts in IP type situations. It doesn’t really work. Please see Against Intellectual Property (which you can also download, print, and distribute (for a profit, if you like)). But really just think about it. How in the world would anyone be able to enforce such a contract? How the hell would the company know where you got it? They could only legally go after the person who breached the contract, and they would have no way of knowing who that was. If they caught you distributing it, they would have to prove they have a contract with you. And even then, in a libertarian society the contract would be unenforcible because there would be no transfer of title taking place…and you can’t force someone to uphold a simple promise.