Valve's always been open source and willing to accept mods and so on. The people who make a living making hats, worst case scenario, would have to pay $20 to get the game, then they could continue making hats.
I also don't think you can destroy the free gaming market, if you're stupid enough to give a 5 year old your credit card details. They don't understand how economics works, you can't make a free game completely free, and people have made other outrageous claims to ban video games as a whole, none of these have come to true though. I wouldn't worry about it.