The Steam and nonSteam clients are exactly the same , this is why you can login on either with either type of account the initial download comes from Steam , but that is for version 2 . 1 and after that all updates to it come via the launcherThe difference is the code you use to register the game . This permanently marks your account for PC as either Steam or nonSteam . Once your account is flagged as one type it cannot be changed . So yes what you wrote is correct , they could still login to the basic game if they were to install the nonSteam client because they are the same , but they wouldn ' t be able to add the nonSteam expansion to their already existing Steam account which was the question . <| sep |> Because it ' s just so easy to point out that it takes on philosophy class to find your logical fallacies . That says a lot about your argument style .