It is possible to enable both the read-only mode of the Zettelstore and authentication/authorization. Both modes are independent from each other. This gives four use cases:
Zettelstore runs on your local computer and you only work with it.
Zettelstore is accessed remotely. You need authentication to ensure that only valid users access your Zettelstore.
Zettelstore present publicly its full content to everybody.
Nobody is allowed to change the content of the Zettelstore, but only specific zettel should be presented to the public.