Many people failed to realize the definition of Free OS in linux is "Freedom" and not "Free of Charge". You CAN sell linux for a price, but you have to provide the source code to your customer as well so that he/she has the freedom to do whatever he/she likes with it without any limitation. That makes you truly "own" the software.
Linux is a bit of a paradox. The OS is supposedly free, yet the tech support companies (the same people who make the free software also own) charge huge amounts of money to get the over complicated programming to work correctly.
Also I would like a Linux fan to tell me, why are companies allowed to sell Linux for more money than Windows ?
When you're buying a Microsoft's product, you DON'T own it, you are just buying the "rights" to use the software.