hi,
If your host requirers you to prove you have a valid licence then provide them with the email you used to purchase your licence and tell them to email
sales@vbulletin.com they will reply with a "yes this is a valid customer" or no if you are trying to host an illegal version but in that case i wouldn't get in touch with vbulletin at all .....
i'm not sure if they do it this way but in my thoughts this seems to be the only "reliable" way since nobody got the right to ask for your Licence number nor customer number.Never give this information to anyone
I just asked my host if they had a problem with vbulletin on there servers.They told me as long as you are licenced No .....