They’re free and available to everyone. Because each name is tied to a pubkey, there’s a unique one-to-one mapping, which means there’s no competition for names (aside from vanity generation). The DNS system is fully operational and can be utilized by anyone in Nostr, as long as it’s supported. Nomen is a solid solution too, and it can be layered on top for those who want it, adding even more options. Think of it as the icing on the cake!