Source Engine 2 doesn't have hidden costs or royalties - but is Steam exclusive

Three major engines went free at GDC 2015, and each of them is monetising in a different way.

There's been a heck of a lot of discussion about development tools and the costs associated with them during GDC 2015. First Epic announced that Unreal Engine 4 would be free, bar royalities on successful releases.

Then Unity 5 was also revealed to be free, with a subscription fee or one-time payment - and Unity CEO John Riccitiello threw some shade at Epic, describing royalty schemes as "f**king around".

Finally, Valve quietly announced Source 2, its highly anticipated engine upgrade, and again said it would be entirely free.

So how is it going to make money? Well, speaking to Rock Paper Shotgun, Valve's Erik Johnson confirmed that games made with Source 2 must be released on Steam.

That doesn't mean they can't be sold via other distribution channels - Valve isn't being draconian - but you can't make a game in Source 2 and then make a fat profit off it somewhere else while ignoring Steam. Valve benefits by taking the slice it receives from every transaction on Steam, you see.

That's not a bad system, really. Valve earns some money for its efforts, but it's the same money it charges everybody who uses its massive distribution infrastructure - you'd pay that no matter what game development tool you used. On top of that, you get access to Steam's other services - DRM, multiplayer matchmaking, Steam Workshop, and much more.

The only downside I can see is if you're a strictly anti-DRM developer and don't want to put your game on the biggest PC storefront in the world, or staunchly refuse to pay Steam's cut, which is higher than some other distributor's. Otherwise, it's pretty decent of Valve.