A lot of people contributed to ActivityPub, but I'm going to give a breakdown of the authors and what they did:
- Evan Prodromou designed the core prototol, derived from the federation API of Pump.IO (itself a "lessons learned" from his experiences co-authoring OStatus, ActivityPub's predecessor)
- @erincandescent converted Evan's set of notes into the spec format and language style
- @tsyesika was the first major editor of the spec once it was being standardized at the W3C
- @rhiaro separated out client-to-server support from server-to-server support and made many, many edits
- And I carried the spec through probably the majority of the bureaucratic process and tried really hard to get inter-project buy-in on its ideas. And most importantly, I wrote that "Overview" tutorial at the top of the document, which is the part I'm most proud of!