Hi There,
I have the same problem. I saw the game on Steam, played the demo liked it very much. Bought it as a gift to 3 of my friends and then one of them returned back the favor so I did not have any option other than Steam. Also since I think Steam is a great platform, I would prefer the Steam way if the site did not give an activation code.
Nevertheless I have the Steam version and I'm an Ubuntu fan so I want to be able to play this great game on my Ubuntu Linux. Also the musics are great so I want to be able to listen them on my mobile phone while I'm out.
If you consider that Steam users have also paid the same amount of money, simply saying "no" to these kinds of requests is a bit unfair. I mean World of Goo did this in the past. Then they stopped because of the fraud but I think this should at least tried. I believe if I go to 2D Boy and tell that I really want to play that game on my Ubuntu, then I can prove that I own the game by simply giving out my Steam Account ID and E-Mail(Steam started e-mail verification). I also believe that you guys are not that heartless to discard this kind of kind request so I'm simply asking for the Linux version and the soundtrack. My steam account name is madBYK and you can see that I own the game from
http://steamcommunity.com/id/madbyk/games