The ActivityPub service is brand new. We are hosting it, and allowing anyone to use the hosted version for free up to a certain limit.
All the source code is also freely available, with docker files that show how to use it. You are welcome to self-host it yourself but you are EARLY - the self-hosting solution is not fully documented or tested yet.
We could have kept it closed source and tested it privately with only invited users for several months and risked the backlash for it not being open, or we could open it up early and have the whole community help get it polished. We chose the latter.
The ActivityPub, Analytics, Docker config and Documentation repositories are all open source and we welcome contributions and constructive feedback on what’s needed to get it “ready”.