Hi, you can download the game from here, just go to download and click on "I already paid for this". The 2.0 version is the one that is on steam but without the steam integration, for obvious reasons, but the game is exactly the same. Also I am working on a new update for the game that I will realesing on steam and here too, when I do that you just need to do the same again, just look for the "I already paid for this" option and download the files.
But if you want to have the game on steam then you have to buy it there.