A nice little look into how open source companies can make money, a year or so ago I doubt crowdfunding would have been seen as a viable option.
One option that isn't mentioned but its the way Ayende Rahien does it, is that you make open source products then make a fortune of training programs that cost and arm and a leg. Ok its probably not a fortune but he's doing alright. I'll let it slide as RavenDB is so well made.
There are certainly a wealth of examples of open source solutions that are free. However, we live in a world where money matters, so open source wouldn’t be nearly as popular if there was no money to be made in it.