Scroll down the page and put in an email address. You will need to make an account on the site and click a link in the email that brings you back to the site where you can download the game via your account page. It is available for Windows or Mac OS X.
This is a flash game (with integrated Flash Player software) and, while there is a free version available on the net, this version is slightly different and includes radar and some minor differences in play that I could see.
It is not redeemed via Steam but I was able to easily integrate it into Steam and was able to easily find a 256x256 icon on the web to use in the Steam library screen instead of the Flash player icon.
I'm not directing this towards you specifically, OP, as it may be a coincidence, but I do believe submitters should credit their original source.