Jason Bessey: Rothbard of course did a lot to popularize the term “libertarianism” in the US, and to spread the idea that American libertarianism was a body of ideas and a political identity radically distinct from the emerging political conservatism of Buckley, Kirk, et al. But he was not at all the first person to use the term in the US. Here’s Benjamin Tucker using it in passing in the 1880s, for example: http://fair-use.org/benjamin-tucker/instead-of-a-book/liberty-and-the-george-theory, http://fair-use.org/benjamin-tucker/instead-of-a-book/a-libertarians-pet-despotisms (he also used it to translate the term “libertaire” in French Anarchist writing, e.g. here: http://fair-use.org/benjamin-tucker/instead-of-a-book/state-socialism-and-anarchism). Charles Sprading’s LIBERTY AND THE GREAT LIBERTARIANS (first published 1913, http://archive.org/details/libertygreatlibe00spra) was published before Murray Rothbard was born, but it was later circulated pretty widely in laissez-faire circles in the 1950s and seems to have contributed to the uptake on the term by Rothbard and a number of others in the late 1950s and early 1960s.
Daniel Baber: I agree that “Intellectual Property” is a government-sanctioned monopoly, and that it ought to be abolished. But Rothbard did not. He opposed patents, but he specifically defended copyrights as a “prosecution of implicit theft.” (He also thought that in a market of total liberty (as he understands it) “Part of the patent protection now obtained by an inventor could be achieved on the free market by a type of ‘copyright’ protection.” See Man, Economy, and State, here: http://mises.org/rothbard/mes/chap10e.asp#7._Patents_Copyrights.
I am glad that contemporary Rothbardians have more or less unanimously come out against “Intellectual Property” restrictions, and have come to see that these are in fact government privileges, not protections of any legitimate property right. They’re right to believe that. But this is a new development, and in fact a reversal of position that has happened pretty suddenly and dramatically (over the course of the past 15 years or so). There’s no basis as far as I can tell for projecting the belief back onto Rothbard himself.