Well, unless the guy has paid for the license from his own pocket, i would like to warn you that :

OVH regularly keeps a check on all the WINDOWS SPLA licenses installed on its DC and if that license is fraud or unpaid for, YOU ARE LIABLE FOR THIS not the owner.

So, in this case the TECH CONTACT which is you will be liable for this, your servers will be suspended and you will be liable for the WINDOWS SPLA LICENSE FEE which you have been installed being the tech contact.

And your seller is free from any CONTRACT coz your name is on tech NIC.

Of course, how i know this coz i had done RESELLING in past few months and 2 of clients of mine tried to forge the licenses and got caught for the same and had to cough out EUROS for the same.