I'm gonna wait for Steam version
Free work is ok if it's not-commercical project, such as modding for game. If it's commercical and they're going to make money off your work then it's unfair.
FreePBR.com is a site full of quality texture maps which are all about PBR workflow. The creators of the project are willing to support indie game developers with free content.
The textures map sets are free to use in your games with no cost involved. Even if you make money off your video game, it’s all free. The only restriction here is that you may not redistribute these PBR file sets on other sites, file sharing sites, email, and so on.
What you get is a zip file with a normal map, albedo map, roughness map, metallic map, ambient occlusion map, and height map. These files are said to be set at 2048×2048 pixels in PNG format. The developers also used the PBR UE4 workflow which uses a roughness/metallic workflow. And, of course, you can use these sets in Unity and CryEngine.