If nature has made any one thing less susceptible than all others of exclusive property, it is the action of the thinking power called an idea, which an individual may exclusively possess as long as he keeps it to himself; but the moment it is divulged, it forces itself into the possession of every one, and the receiver cannot dispossess himself of it. Its peculiar character, too, is that no one possesses the less, because every other possesses the whole of it. He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me.
A quote from Thomas Jefferson in an oldie but a goodie essay, especially relevant given all the talk about GPL-based business models the past few days: The Grand Unified Theory On The Economics Of Free by Mike Masnick. (Before anyone says it: the GPL doesn’t say you have to give away anything for no-cost. However as a businessman myself, I think it’s an excellent approach sometimes regardless of license.)