Does the open source version of anvil server, can it use shared databases, or is it one database per app? I found this in the documentation, and I was wondering about it.
Every app, open source or not, can share tables from other apps.
I think the database that snapshot is talking about is the database the server is working with, while the database you are talking about is the database inside an Anvil app configuration. All the databases used by all the apps on your account (or on your open source server) are stored in the same Postgres database.