It's battle of the engines at this year's GDC. It's a war on two fronts: prettiness and price. In other words, what will the engine let developers do, and how much will they have to give up to do it. Unreal Engine 4, for instance, is now free to use, but requires a 5% royalty on gross revenue over a small allowance.
So how about Valve's new Source 2? Talking to RPS, Valve's Erik Johnson explained that Source 2 would be free for developers, and that there would be no royalty charge for using the engine. There is, however, still one catch. Games made in Source 2 must be sold through Steam.
That means that Valve will take their standard 30% cut for Steam distribution. Crucially, Steam doesn't have to be the exclusive distributor. Source 2 developers will be free to sell their game wherever they like, even directly, as long as they also sell through Steam.
That seems like a pretty good deal, but it's one that raises a major question: if Source 2 games must be sold on Steam, does that mean that Source 2 games instantly bypass Greenlight? If so, that could be an attractive bonus for developers looking for a guaranteed place on PC gaming's biggest distribution channel.