You know this same claim was brought up by Activision against Valve, who in turn said 'What the hell are you talking about?"
Valve does not have a monopoly, a monopoly would be Valve making all the profits and desginers being FORCED to work with Steam, no one forces a developer to do so, and though I am not sure (maybe Larian can confirm or deny) but Steam allows you to use a distributor and get a much larger profit back as Steam wouldn't charge as much as say EA would per copy to distribute your product.
