If OVH wants to take Ubuntu and call it OVH Linux, they can do that.. and they won't need to pay Ubuntu anything.
OVH is being asked to pay for a license because they refuse to rename it, and they refuse to distribute it unmodified.
OVH could also distribute it unmodified, and then package their changes into a deb package that they tell customers to install. Or they could simply allocate severs depending on which OS a person selects (so Ubuntu will work unmodified).
The fact is, they have several options to comply with Ubuntu's trademark policies.. but they've chosen to do none of those things.
"Re: Debian images on Microsoft Azure cloud" https://lists.debian.org/debian-cloud/2015/11/msg00099.html
Disclaimer: I am not a lawyer, and I'm not affiliated with Debian (other than being a long-time user).
See also:
https://wiki.debian.org/Teams/DPL/OfficialImages https://wiki.debian.org/Cloud
and more generally:
https://wiki.debian.org/Teams/DPL/Trademark
[ed: As for the "upcomming policy" mentioned in the email linked, I think this is still an ongoing process, but it more or less boils down to the wiki-pages linked. IIRC one of the issues with the initial Azure effort was that the scripts generating the images needed to run on Azure - so couldn't readily be re-created by just anyone.]
How much to they pay Debian for using a modified version of Debian?