The Secondhand Licenses section now verifies licenses being sold whenever possible. At this point, it's only verifying ownership and transferability of XenForo licenses since they have an API for it now. If other software publishers start making verification APIs available, we can also incorporate those in the future. Long story short is any XenForo license listed for sale from here on out is one that the system validated that the seller owns it *and* that the license is eligible for transfer.