I am trying to add a couple of friends who also joined up for a beta invite on the main site (and they connected with FB) but I cannot add them in to the game. Is there a waiting period for them to be available for invitation or is this a bug?
Oh, I misread your question! And I'm still not sure what your question is, but I hope the following help....
I suggest that you tell your friend to sign up on www.glitch.com and then jump the queue at www.glitch.com/fans. FB invites seem so much trickier to me :P
Good luck!
If/When they are already in-game, you can add them on their profile page after searching for their username here: http://beta.glitch.com/search/