> I'm not sure that 'decentralized' in this case means decentralized in community.
The idea of ActivityPub is to have a federated group of servers. Similar to XMPP and Email.
So you can create an account as Alice@serverAlpha.com, while I can create an account as Bob@serverB.com. When I publish a video at serverB.com, it will notify serverAlpha.com that a new video was published, which eventually tells Alice to check out the new video.
> However, this does resolve my concern about 'instances'.
On a surface level, it should. But given what I've seen over the past 15 years, no... it shouldn't resolve those concerns.
Consider if Google / Youtube became PeerTube compatible with ActivityPub next year. But then, there are additional features that only exist on Youtube's implementation (spam monitoring, Twitter integration, Youtube integration, etc. etc.). Something that makes people prefer Youtube over other hosts.
Eventually, Youtube can cut out ActivityPub, after it captures the ActivityPub marketplace.
See XMPP and Google Hangouts if you want a historical example. Embrace, Extend, extinguish is the name of the technique, and it is quite effective at killing open standards.
The idea of ActivityPub is to have a federated group of servers. Similar to XMPP and Email.
So you can create an account as Alice@serverAlpha.com, while I can create an account as Bob@serverB.com. When I publish a video at serverB.com, it will notify serverAlpha.com that a new video was published, which eventually tells Alice to check out the new video.