The horror!
I was reminded yesterday of the policy of official add-on licenses with XenForo.
Purchasing the official Media Gallery or Resource Manager, which are legitimate addons, marries that license to the forum. It can't be transfered to a different one you own, or transfered to another customer.
I think there is some weirdness in how long the support is for the add-on. I think it expires when your XenForo forum license expires, no matter when the add-on was purchased.
Seems like a draconian way to license a product, but maybe it'll change with 2.0. #WheresKier?