Ed Key, a developer of Proteus, told Game Informer that he was able to confirm Fast2Play's selling of Steam keys obtained from Humble Bundle purchases. Key discovered this by purchasing Proteus through Fast2Play, then comparing that Steam key to an inventory that had been sold through Humble Indie Bundle 8. Key has since succeeded in having Proteus removed from Fast2Play and some of its sister sites.
Game Informer points out that Fast2Play is also hosting sales of Steam Gift versions of Awesomenauts and The Binding of Isaac. While that doesn't affect charitable proceeds, Steam Support states that "any accounts tied to a redeemed gift from a fraudulent source may be suspended." This possibility is noted in the "Activations Details" section of its Steam Gift sales, which asks customers to "please remember you are doing it at your own risk!"
A 7 Entertainment representative has responded to the story, explaining that it was "never in our intention to expose any indie developer to any financial losses." The representative states that Fast2Play is an e-store with products from official suppliers, adding that it's awaiting an explanation from the distributor of the involved codes. The representative also described Kinguin as "an Ebay for gamers," explaining that Kinguin itself does not own those keys.