Info on how to get your Steam key and what will happen with your previous save data.
How to get your Steam keys
If you already bought Goscurry via Desura, the Humble Bundle widget, the Brandon Boyer Bundle of Love or the GamesRage bundle, you will get a Steam key as soon as it's out (you might actually get it even sooner, but the Steam version won't unlock until release date).
How to get it from Desura
Login and go to your Collection. Find Goscurry and rollover its picture, so that the "My Keys" button appears. Press it and voilà, Steam key!
How to get it from Humble
Login and find Goscurry in your Library. From there you'll be able to activate it on Steam (please note: keys might appear a little later than the release time, but surely within the day).
Save data
When you start your Steam version the first time, all your existing save data will be converted so you won't lose it and it can be used with Steam Cloud. That is, unless you last played on a Goscurry version older than v1.2.060, in which case I'm deeply sorry but all your data will be reset (older versions use a leaderboard system that sadly failed and that I had to replace completely).