Ada Calendar is the calendar part of a private voice assistant that the Rutter family runs for itself on its own home server. It lets the assistant read, create, move and delete appointments on the Google Calendars of the family members who have signed in and agreed to it.
It is not a public product and is not offered to anyone outside the family. Each person connects only their own Google account, and only after signing in and approving access on Google's own consent screen.
Details of what is stored and how to remove access are in the privacy policy.