I remember using ReactOS a really long time ago and essentially forgot about it. Dave discovered it recently, told me about it, and I said “Oh yeah! I remember that OS.. I guess it’s still alive and kickin’.”

Yes it is, however to this day it’s still in alpha stages meaning you absolutely should not use it as your primary OS.

What makes React different is that it appears to be a ground-up OS(?)

Definitely interesting and worth a look. See video below for details.