Some info from IRC on the signing up process (when it comes to that):

<~Athena> current plan is the following

<~Athena> 1) if you are in the old DB you can use your old email/username + pass to sign up

<~Athena> 2) if you are not in the old DB but you are on one of the selected trackers (currently PTP, BTN, GGN, EMP, MTV, 32P) you can sign up by proving your membership on these sites

<~Athena> this will be done with an automated referral page we are currently developing

<~Athena> 3) if you signed up to APL after the backup date, you will be able to apply for an invite with the proof of you old invite email

<~Athena> 4) if you joined APL when email was down (since somebody MIGHT have not fixed that for 5 months) we will use other methods to verify your membership

<~Athena> 3) and 4) will be either via IRC interview or an application page on the site, if Spine can get that done on time.