We've uploaded a big chunk of Steam keys on Desura. Owners of I Shall Remain on Desura can get there and redeem their keys.
Here there are the steps to do it
1. After your Login into Desura, go to your collection (http://www.desura.com/collection)
2. Search for I Shall Remain and click Keys
3. Copy the provided key and add the game via Steam-client from the lower left corner via "Add a game" button.
Let us know if this works for everybody.
Have fun!