Hey, author here. This is built on the nostr[1] protocol which has many advantages over activitypub. I highly recommend reading the readme on the github for motivation on why we would need yet another decentralized social media protocol.
A google search for 'damus social network' has this HN page as its 5th hit. That is pretty impressive for a page created 33 minutes ago, with (as of yet) zero tracktion.
Happy to answer any questions :)
[1]: https://github.com/nostr-protocol/nostr