I'm not sure how Windows counts as proprietary. Microsoft provides an operating system that runs on a relatively large variety of processors and is compatible with more hardware than all the other operating systems available combined. The government tore Microsoft a new hole for including Internet Explorer as an integrated part of the operating system, meanwhile Apple... OMG where do you even start with Apples Anti-trust behavior ! Apple dictates every piece of hardware and software combination and their rigid control of the iOS goes way beyond any tax/money grab on developers ! Apple is continuing to push their marketplace control right onto the desktop.
If someone like Steve Balmer was to even suggest doing with Windows what Steve Jobs has done with Apple, the media and the government would be on him like he had a fist full of kiddie porn. Eventually everyone gets tired of the tyrants, even the apathetic consumers, no one really enjoys heavy handed taxation. Apple's gained a lot of ground by touting their products as flawless (Apple vs. PC commercials) and by association, their elitist position. In reality, for closed ecosystem products, Apples have a lot of flaws (lock-ups, bsod's, vulnerabilities,...) and that "I'm better than you" marketing is going to come back to bite them.
Who knows, maybe Apple will try to revive their image as being the friendly computer and replace Jobs with Woz ... lol ! There's a guy with a dash of genius and the charisma of a chipmunk.