How to buy an Xbox One game that you got for free via Games with Gold

Hi, i searched everywhere for someone else to ask this question, but can't find it. I downloaded Guacamelee! as part of the Xbox One Games with Gold promotion for free on the Xbox One. I played it and love it. I would like to purchase it to keep it permanently.
I understand that if my xbox live subscription would run out, then i would lose access to this game. Is there a way for me to puchase a permanent license for this game once i have it for free? When i go to the store, it says i have already purchased it.

:)

 

Xbox Live Gold Trials

Okay,

This is my second time reedeming an Xbox One free trial code you get with the games you buy. I tried doing so when I had silver membership and got the same reply as the one I just did when trying to reedem via laptop.

"You have gold membership already. Give this trial Gold membership to a friend who hasn't tried Gold, and let them see what they've been missing on Xbox Live"
Surly if I pay for the games I'd want to use the free trials right? You could do so on the 360, so why should I give the free trials away to someone who didn't buy the game? Plus I never had gold membership when I tried reedeming the first time, so why
isn't it let me? I'm not being harsh or anything but if you get freebies inside a case that you buy (especially spending 45-50 pound on) of course you'd wanna keep it for yourself.
So my question is, how do I reedem these codes? Or have xbox put a system in place that Xbox One owners can reedem gold trial's they are giving? Could I reedem them via Xbox 360?

 

Download games with gold

For xbox one games you can buy at anytime with or without a creditcard

However for 360 Webmarketplace purchases you must have a valid payment option on file for your region

It does not affect the price it will remain free bit you must have a valid payment option

Also should be noted that a only the account with actual gold not shared home gold can be usrd to purchase games from games with gold via the 360 Web marketplace

The only other way is via a 360 console

 

If you revert to silver you should then have the option to purchase the game. If you do not then try deleting the game to see if the option to purchase it will pop up.