We plan to allow licence conversion once the XF versions of mods are completed (there may be a small fee of a few dollars to cover the increased support workload which will be caused by the installation of the mods onto a new platform).
As far as selling the licenses goes, due to the nature of PayPal you will always be considered the owner of the licence - the reason for this is someone could purchase a licence, sell it on to a third party, then reverse the transaction via PayPal. This would mean the license would be cancelled despite the third party having paid for it in good faith.
Cosmic