ActivityPub is a messaging backbone with an inbox/outbox metaphor.
The AP bridge is a great demo of a FediClient/Mastodon (inbox) linking to an Activity verb called 'Follow' published from the Podcast Index (outbox) via the ActivityPub protocol.
However that is not what TrueFans is trying to achieve. TrueFans will become a full FediClient with an in/out box for ActivityStream messages.
/cc @wjmaggos @BeAware @tchambers @evan @steven @davidpierce @dave @chrismessina