

Steam Greenlight was a program where independent games without a publisher could release games on Steam, but it was absolutely exclusive. They couldn’t sell their game elsewhere.
Literally the first game released on the program was a free Total Conversion mod that you could download anywhere else for free, but if you wanted to get it installed through Steam, you paid them for the privilege.
I was slightly wrong about the order. I was actually talking about Black Mesa, which was in the same initial batch of 10 games.