I bought it at the KSP store before it was available on Steam, and transferred to Steam the minute it was available. Back when I bought it it was impossible for me to log into the account I had just created because it said the password was wrong, and it was impossible to reset the password. Therefore I couldn't download the game, although I had already paid for it. I torrented with the logic that it's okay to snatch a gumball out of someone's hand if they accepted your money and said they'd give you the gumball in exchange. The KSP store must be much better nowadays, so I would buy it from there again to help out Squad, but I like running it off of Steam for the features.