[citation][nom]Bolbi[/nom]I don't think the parallels hold between credit and monopolies, but that doesn't matter because patents are not monopolies. In the US, they are valid for only 20 years at the expiration of which time they may be extended at the discretion of the United States Patent and Trademark Office. Besides, they may also be sold or the rights to them leased. I would hardly call these conditions a "monopoly".[/citation]
You really don't know the history of the word "patent". The first patent letters have been issued by European Monarchs in order to give exclusive right to ownership and possession of something like coffee trade, gold trade, and etc. (a.k.a monopoly).
When the printing press become widely available the monarchs start requiring a "printing patent" (later it become copyright) in order to ensure that only approved by the government books are printed. (a.k.a. censorship).
http://en.wikipedia.org/wiki/Patent
"As state-granted monopolies, patents have been criticized as inconsistent with free trade. On that basis, in 1869 the Netherlands abolished patents, and did not reintroduce them until 1912."
Just because the patent is issued for 20+ years it does not make it less of monopoly. In fact 20+ years period is like millennium in the fast moving world of the software.