Ugh annoying headline. “Buttonless” implies the buttons are disappearing, like the home button. The articles says they might be using “solid state buttons” which, I think, are a bit like the Macbook trackpads, there’s no real button but it still acts and responds just like a trackpad button.
The lock and volume buttons likely will still be there, just won’t physically move, and use haptic feedback instead.
It may not be de jure open source, but if the code is posted publicly on the internet in a way that anyone can download and modify it, it sort of becomes de facto open source (or “source available” if you prefer).