Doesn't this seem just a little pointless though? I mean, how many games actually have mod tools, or allow modding? Compared to the number that don't, it will be tiny. Although, to be fair, Skyrim is a big one.
Unless.....valve are going to "encourage" developers to release mod tools. "Nice game, it would be a shame if it was removed from steam. I think that you think about releasing the tools you used to make the game. Know what I mean?"
War Raichu, who do you mean by "the cut they get"? If you mean valve, 30% is 30%, the amount will add up, especially with popular mods(or the sheer number of mods sold).
I wonder what effect this will have on Nexusmods.