I always see people who say that open source != monetarily free. While I agree that may be technically true, I think practically speaking it is not.

Why do I say this?
Well to my knowledge there isn't any successful company that makes money by actually selling open source software. There are a few companies that have become successful by selling complimentary services like Redhat with Enterprise support or Mozilla with selling ad space in their browser, but none that actually sell the software directly.