I think the real news is that some people have started to build what might become something like a
"jjhub".
https://ersc.io/
I think 'jjhub' is a decent immediate first approximation, and is often how I've started out talking about it with people. At the same time, we have to offer real value here, as you can already use jj with github (and I have for a long time now), so there's more to it than that. But yes :)