Which to be absurdly clear - is exactly what Rebble did to Pebble. They scraped the apps and are now mad that someone else could do the same to them.
If Core were to do the same thing here, it's not the same, because Rebble is still active. You can't kill what's already dead (Pebble), but Rebble is very much still alive.
This seems a little silly, no? rent seeking behavior for maintaining code they didn't write to begin with?
They're entitled to it just because in some sense Core is a successor to Pebble? No, not really.
No one's actually entitled to anything here on either end (legally), I see 0 work being done to actually contact the original authors to seek permission or licensing details.
AFAIK, there wasn't a blanket license that covered all apps in the ecosystem... so each app would vary. In the absence of a license all rights are held by the original developers.
Again, if that's all it were, Core could and should just take that old Pebble dump and use that. Why bother Rebble if they haven't done anything as you imply.