[paulmd]

Microsoft doesn't get a cut of Jetbrains' IDE "mod" revenue, though, despite the fact that Reshaper and similar products "piggyback" (what a loaded term) onto Visual Studio and other Microsoft products. Microsoft already got their cut up front.

Same thing for Bethesda - it's not their value-add and they don't have a moral right to take a cut. On the other hand Steam is providing a value-add here - a market and financial transaction services.