I don't believe for a second they'll let just any old person sell their game through steam.
So at best, they allow anyone to use this, but all it does is install the game on Steam after you've sold it through your website.
So at best, they allow anyone to use this, but all it does is install the game on Steam after you've sold it through your website.
This aspect is cleared up on their webpage:
Steamworks is not engine specific and will work with any underlying technology. Whether you're publishing your games on Steam or not, Steamworks lets you take advantage of Steam features in retail products.