I know, since I've been telling you that all along, but you were once again suffering from schizophrenia and were for some reason arguing about it.
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.