I was just tipped by @Nazanin (thanks!) that the old Stan Google Group cannot be accessed by people who are not members. While logged-in into my main Google account, I can read all the contents of the group. While logged in into another Google account (or not logged in) I see this:
This seems unfortunate as the group still contains a lot of valuable and relevant discussion. I am not sure who manages the group, but could it be made read-only accessible to everyone?