HarfBuzz is maintained by Behdad Eafahbod who _used_ to work in Google and Facebook.
Doesn't matter who maintains it. It matters who owns copyrights.
That doesn't matter, since it's FLOSS with an irrevocable licence. That's the great thing about free software.
That wasn't the point. Yes, you're free to use it. But many of us would like not to depend on Google code.
If you read that license, you'll see it's free software. Anyone can fork or maintain it just like was done for over a decade before Google and Facebook were involved.