It uses an HTTP/JSON-based DVM. A competitor should investigate exposing the exact same API under a different hostname and then clients could decide to implement support for both at the same time without having to write two different integrations.

I'm confused, why would you do that? npub.world is a product for end users. If you want to compete with it, you can use Vertex DVMs (or any other) from client, server or wherever you want.

ofc not. It's my client, and its sole purpose is to showcase Vertex.