Really great overview!!  Super helpful reference having all of these in one place :)  Thank you!

This was more to figure out the proper way to do this in order for tracking for the badge, etc on the G.M. platform.  It makes sense that it needs to originate in a challenge (and than you to Olga for pointing that out).

I don't think that just having a form on the D.C. to invite a friend necessarily makes sense, as anyone can just shoot a friend an email with the link.  If others would like to see this as a new feature I won't object though.

Thank you @Olga Zavrazhnova!  I knew I had seen it somewhere at some point.  I just had a conversation with a new colleague yesterday about the value of the D.C. and Global Masters, so I will send her an invite :)