I use Drupal Commons 7.x-3.12 (uses OG 7.x-2.7). There, I have a private group with private posts. (Means, the group node uses privacy settings "Joining requires admin approval" and "Hide contributed content from non-members").
I want to make this private OG group public, and all content nodes in it.
So I tried and set "Privacy settings: Any site member can contribute" when editing the group node, and rebuilt the permissions. This made the group node publicly visible, but none of its content nodes – neither those created before nor after this change.