Just for the heck of it I ran a check on the domains for the users that have validated their license on my site. I found that a small group of the domains are not resolving to any host, but I know many of the users have active sites on a different domain.
Is not having a valid domain registered with a license against any XenForo policy or does it not matter?
I agree, that's why there's now a big warning on my site about this. If the site that's on file on my site is not valid and they try to download a premium add-on, people will have to revalidate their license.