@fediverseconnection@social.vivaldi.net according to y4my4m, they've been working on it for years. The core application they've completely built themselves. By they do admit that the UI, placeholder art ( which they'd like to find an artist to replace it eventually when they can be paid ) , tooling, etc is LLM assisted.

In that thread you link, silverpill, indicated that y4my4m has been working with the social working group on expanding ActivityPub.

Totally understand this will turn some folks off, but honestly, I think this is worth that trade off to me personally.