In your member area at vbulletin.com click on the priority support link, in there it gives you space to add on 3 other email addresses. Add your other admin's email address and make sure he signs up here with that address.
Yes, Jelsoft allows up to 3 names per account (in addition to the owner). The instructions have been provided. Doing this will put your administrator as a licensed user in the eyes of all vBulletin.org activities allowing them the same access as you.