"Projects outside the kernel began adopting Git shortly after its release. A key landmark in Git adoption came when Keith Packard, one of the lead developers of the X Window System, published two influential articles in 2007."
It's exactly what it sounds like.
Looks like a successor to Blosxom and PyBlosxom and maybe also IkiWiki.
I swear I remember this diagram from the GNU Arch days.
Stet is a cool piece of software that was used in the GPLv3 process. I think there are better tools now, but it's nice that the code is now easily available online.
I agree with all of this except the suggestion that Torvalds is responsible for it. He popularized this model of development, but he didn't invent it.
I strongly suspect this will come in handy soon.