Sell Items for Non-Valve Games on Steam Workshop

Valve announces a milestone, saying they have paid out over $50 million to content creators since they launched the Steam Workshop. They are marking the occasion by releasing new tools and adding item creation and sales for games by other developers:
Since the Steam Workshop launched in late 2011 over $50 mil has been paid to the community content creators producing items for Team Fortress 2, Dota 2, and Counter-Strike: Global Offensive. To celebrate and expand upon this success, Steam content creators now have the ability to create and sell items for non-Valve games. And in addition, a new suite of reporting tools have been introduced that allow content creators to monitor and track the sale of their items in real time.