Hi Mason, I had confusion too since I had already owned the commercial version before the Visual 2008 & Dark GDK combo came out. I dont know if this the same with you or if this helps any...
The Dark GDK that you download with Visual 2008 is the latest version of the GDK. So at that point, if you already own the commercial version... then you have nothing to worry about selling your games. I say that since I was confused about that whole point. I didnt know if Dark GDK we download with visual 2008 was "only" for freeware use.
When you install the Dark GDK, wierdly, it does install the EULA and that .exe to the "Game Creators Dark GDK" directory. Run the .exe after you have install visual 2008 and got it going. Then it will install Dark GDK and it's wizard as normal.
Looks by your post, that last step I mentioned could be all you have to do now.
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