"Several people have asked about using #ActivityPub if you're hosting #Ghost elsewhere. Some quick notes about that:
Importantly, Ghost's ActivityPub service is already out in the wild, #opensource, and released under the MIT license. We build in public, and all our work is up on GitHub for anyone to download, fork, run or deploy if they want to."

https://activitypub.ghost.org/warp-factor-5-mr-sulu/