As you can see here: https://xenforo.com/contact/ Xenforo has a report-formular for pirated versions. As @Stoker mentioned when your site gets reported they will contact your host to take down your website, what happens then depends on your hoster and his policy with nulled scripts.
There are hosters that call themself "off-shore" - they won't give a flying f about any copyright infrigment, as long as it doesn't harm them - when it gets to much or they get a charge in their contry they might abandon you. In Russia or Asia there are many of these hosters - but even inside the EU you can find hosters that allow nulled scripts.
If you want to be on the save site: buy a big server as backend, and a second, smaller server, as frontend and then redirect all traffic from your backend to the front. This way, if anything happens it will only be your front server that gets taken offline, and you can just get a new one somewhere and be back online in less than an hour without any files loss or need to revert to a backup.
I didn't mention that you use fake personal data and payments to register any server, but that should be obvious
greetz