...specifies whether a BlackBerry device user can forward a BlackBerry� Messenger contact to another user.
Edit: Nevermind. Pretty sure that is something else.
Now, I too would like to know. If I find anything else I'll share.
Edit #2: I guess the Help icon really does help. Here's what it says:
If you turn off invitation forwarding, contacts that you invite can only accept invitations from the original email address or PIN that you sent the invitation to. If those contacts try to accept the invitation from a different email address or PIN, their acceptance is rejected.