Unless the tech demo is a custom engine using assets from FF15.
ever since the earliest EULA/TOS you have only ever owned a licence that was non transferable, just until recently it could never be enforced, so nothing has changed other than the security software.
Keep in mind too that even if EULAs are found unenforceable, in the DD market you are not selling products, you are selling services. That is, you are selling to an end-user an authorization to receive a digital product through a game store.
As part of the terms of service, this service you purchase is for your own use only, and cannot be transferred to another person.
There are Steam Gifts, however, that is only for one to gift the service to a friend and not authorized to be re-sold for a profit.