I contacted vB support back in December of 2002 to ask if the vBulletin copyright info was necessary on other pages that included vBulletin files, but were not created by Jelsoft. Steve answered the ticket and asked for me to give him some examples. I gave him the homepage and a couple of others on my personal site and his reply was this:
Since these are not vB generated pages then I don't believe the copyright is absolutely necessary. I'm not sure I understand your desire to remove it but that's your call.
So that's what I've been going by and told others the couple of times that the question has come up. If this is no longer the case please let me know so that I can be sure to give the correct information should the question ever come up again.