If a Jira Service Desk portal-only customer (unlicensed user) tries to access an article that contains a Team Calendar in an integrated Knowledge Base, the user can see the calendar but not its events.

This happens because Team Calendar will check if users are licensed.

If the Confluence space is public (allowing anonymous access), and a non-logged in customer accesses the article through the Knowledge Base, the Team Calendar events display correctly.

If the customer (that doesn't have a Confluence license) logs into the customer portal, they see the calendar (and a 401 error) but stop seeing the events.

Suggestion:

Start considering Jira Service Desk portal-only customer as Anonymous access, so they can see calendar events in KB articles.