You nicely leave out the end of that sentence, "built on open source software," in order to misquote me, one of your usual shady tactics. Although more correctly instead of "OS" I should have written "shell." Open source does the heavy lifting in OS X, the proprietary stuff makes it pretty and brain-dead easy to use.
OSX is still a proprietary operating system no matter how many qualifiers you want to throw out there. Apple's relationship with your freakish "community" is testy at best. You're really going to hate them when the lawsuits against these open source hackers start actually getting filed.