My understanding is that: OStatus is a decentralized social networking protocol made up of several other protocols (Atom feeds, Activity Streams, PubSubHubbub, Salmon, and WebFinger) GNU Social and Mastodon are two server software applications that implement OStatus pump.io API is an interface to the pump.io server software (Activity Streams, OAuth, Web Host Metadata) identi.ca is a pump.io instance (not accessible right now), GNU MediaGoblin is a server application that currently uses a pump-like API ActivityPub is a proposed decentralized social networking protocol GNU MediaGoblin is a server application that will likely implement ActivityPubHow do these protocols interoperate? Does ActivityPub completely replace OStatus, or only the Activity Streams component?