Except patents are a government creation. The corporate world rests upon government intervention upon their behalf.
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Not by any consistent or sane definition of the term.
Like all political labels the term is abused (as is the term free market - most 'free market' advocates don't advocate anything close to it).
The most commonly accepted definition of libertarianism is political thought founded upon the Non Aggression Principle - that is, it is immoral to initiate aggression against another.
On those grounds, consistent libertarian thought opposes patents and copyright as arbitrarily enforced by an aggressive state. Free software on the other hand is a great example of decentralised, voluntary organisation - the very essence of any libertarian society.
That's not to say that there could not be software licenses - that's possible, but they'd probably be unenforceable.
For some more consistent libertarians who embrace open source/free software and apply it in their own work, try c4ss.org.