Sharepoint Online - users access without licenses

I read the post (after submitting my question on another thread) and thought I might try posting my question here in the hop eof a better response :)

I have a query around the licensing for internal users within a specific scenario where SharePoint is not been used directly but only there as a data source for another custom made web solution.

Let me explain, say we have

1) Installation of SharePoint or purchase of SharePoint online at http://mySharePoint.

2) A custom web application http://babyIntranet running on asp.net and using a low privilege service account to pull information from SharePoint like lists or document libraries.

Any internal users accessing http://mySharePoint will need a license (online) or CAL (on-prem),understood. I will merge the terminology of CAL and license for the rest of the question.

But what about internal users only accessing http://babyIntranet, they are not technically using SharePoint just the web application (which incidentally is querying SharePoint with a service account). Do these internal users need a SharePoint CAL?

In addition what if a background service was copying data from SharePoint to a separate database and http://babyIntranet was using that database as a data source. Surely then internal users would not need a SharePoint CAL for using http://babyIntranet ?