It's entirely visual in that it is a graphic of a vocal tract where you can move the tongue and shape the mouth, so in that form trying to make it do anything with screen readers would mean basically doing what the second link does, and create an API for it and hook the backend up to an entirely different UI.

The videos on the other link does show that the guy who has done that API has done stuff to the UI to allow interfacing to it in non-graphical ways, but sadly I don't see any online demos of those alternative user interfaces anywhere, which is a great shame. Sadly it doesn't look like the videos are very accessible either, as they're mostly demos with no commentary about what is going on on the screen, without which they're mostly just random sounds.