The Nostr protocol can be split into 3 separate interoperability layers:
1. Core event data structure with canonicalization, hashing, sign and verify operations
2. Relay network publishing, filters, and authentication with expected client/relay behaviors and event kind ranges.
3. Event kind registry: kinds, common tags, expected behaviors, encrypt / decrypt operations, etc.
There is only one way of implementing 1. This is what defines Nostr as a social-first protocol and the reason we are all here.
There are a few possible protocols for 2. The relay network is our layer-1, but there will be others.
There are thousands of options on 3. Here is where apps shine.
GM.