jamotide: Its definitely not the steam key, I sent that one now as well. But we got some sort of workaround now where I sent him the download link from the humble store for the standalone version which can be used with the chrome key. And I think he can also still tradeaway the steam key. Anyone know? That would maybe make up for the troubles.
Much appreciated, but the download from the link was fine. I'm rather fanatical against DRM, so it's unlikely I would ever use the other keys. So feel free to give them out if you like. I've got that game itself so I'm content, thanks!
I marked the first reply as the answer, since it is technically correct, even though inapplicable to our own trade. It's all good advice, and I know more about how Humble Bundle purchases work too. All goes towards making me (and hopefully others) a more informed buyer and trader.