A lot people has been asking about Steam keys.
So to break it down, it works like this. If you have the game on Desura or have a Desura key from a bundle you can get a Free Steam Key.
All you have to do is redeem your Desura key on Desura and go to http://www.desura.com/collection and get you your Steam key. This won't work till the game is released, so check Steam to see if the game is available first.
Hope this clarifies things a bit :)