It's still under active development, though I've temporarily handed over the reigns to others while I've been busy getting the federation standard we're going to use nicely shaped up through the W3C spec process https://www.w3.org/TR/activitypub/
That's taken up more of my last year (okay, last two years) than I expected. I'll be back in the swing of things within the next few months. We have a federation branch right now, but the standardization process of ActivityPub meant that we're going to have to retool some things before its released in 1.0!
The good news is that ActivityPub is looking to be picked up by projects like NextCloud, Mastodon, Pump.io, and quite possibly GNU Social, Diaspora, postActiv. This means we should be able to have more federation working across the many federated social web projects out there.
If you're interested in ActivityPub and federation generally, I highly recommend checking out the tutorial, which is baked into the spec: https://www.w3.org/TR/activitypub/#Overview
In the meanwhile, Boris Bobrov (breton) has been kindly doing the main work along maintainership while I've been preoccupied. But, I'll be back soon... and it'll be good to be back!