Key from Humble Bundle's new game making bundle.
If you need to know more, go read up on humble bundle's website.

I already have the software and this is an extra so take it off my hands, won't you?
Good luck.

Due to my idiocy for listing only software key and not the premium DLC key and that the dlc cannot be listed separately, I'll add on steam and send you the DLC key later. Please note that the dlc key is not any of the additional DLCcs listed in store because it originally comes together when buying the axis game premium bundle on steam.