They actually sell a service where you can buy a domain name and have it set as your username.

It’s not centralized, it’s also not a federated network like AP. It’s just a different design.

Not quite true. You can host your own personal data store (PDS), run your own labelling service, and you can host your own feeds.

The big relays and app views are the only thing that aren’t really supported by the official app yet.