APP PUBLISHING is not REQUIRED, but is RECOMMENDED. In order to use Push Notifications, your app MUST be published to an app store.
Note: Apple charges a cost of $99/year for the apple iOS Store publishing (this is not a charge by us, and one we don't have control over).
For Google Play (Android Store), the charge is $29/year.
If you decide to NOT publish to an app store, you will be using a FREE Progressive Web App, and everything will work EXCEPT Push Notificaitons.