In response to all the comments saying "hey, they'll give you license keys!" - I'm afraid some of them won't. My recent client was very access paranoid and I wasn't given much to play with in terms of webspace, and the same was true when he asked me to mod his vBulletin forum.
Why would your client be access paranoid? Just tell him/her to add your email address you used to sign up with here on vB.org, and be done with it. The system will update and vBulletin.org will automatically allow you to start downloading plugins.
There is no reason for your client to be access paranoid. That's just silly, unless your client is nervous to log into his own members account.