As there still not an affilaite system set up for itch.io. I have this idea I would like to share.

This affiliate idea can help  developers to gain more revenue. For this affiliate system to work the affiliate must be humble and be willing to split their profits with the original developer. 

1.  Download the game you want to sell. Make sure it is an Unity game. As you can easily re-zip an Unity game (am not so sure about other system games) and give it to someone else. Also, I find the free games are much easier as you can just download the game, and also most developers of free game have a 'support me' donation box. Prehaps paid games will also work but I could not find the 'donation box' (as in just giving them money, after all you would probably already paid for the initial download). 
2. You probably need Dropbox or similar to clould share the zip you just created
3.  You probably need to have to set up a PayPal BUSINESS account (see PayPal on how to do that) to gain access to the buy now function. 
4. Give a price for your 'merchendise' (in this case is someone else game). Never put $0 as you want to make money for yourselve and the developers you uncondionlly helping out.
5. Inside the create buy now button, there should be section which said 'if buyer paid successfully, sent them here' ~ post the Dropbox link to the actuall game there. 
6. Create a Facebook PAGE, so that you can use Facebook ADS. That's right use Facebook ads to advertise your 'merchendise'. Now I am not going to teach you how your should do it nor how you much you should budge the ads cost. However, do remember to put that PayPal buy now link somewhere in your ads. 
7. If you make a sale, give at least 50% to that game's developer. (This really depends on what kind of people you are). 

Hey, thanks for the ideas. We will never permit people to resell others' games on their own accounts. If you download someone else's game and try to sell it, even if it's originally free, we will suspend your account. Sorry, but that's stealing.

In the future we will have a way for developers to allocate revenue share to people who bring buyers to the existing page. We already have an affiliate attribute system set up for press account holders, but we're going to make it more generally available and open the payments portion. Hoping to have something out within the next few months. 

Thanks

That's seem fair enough but how would you stop someone from reselling not in their Itch.io account but other places (i.e. reselling it in their Shopify for example)?