I'm guessing the demo uses HTML5 features that are only currently supported by Safari. So in principle it is open, it's just that other browsers still have to catch up in their HTML5 support. It's the typical Apple approach of embracing technology before it's quite mainstream, and abandoning other technology in anticipation of its becoming obsolete.
So yes, open, if and when the world catches up. And open because the world *can* catch up – Apple isn't using proprietary tags, so there's no reason other developers shouldn't build that support into future versions.
Still, for now, it's more exclusive than inclusive… not really surprising though.