All PBR materials, brushes, photos and 3D models offered for download on CC0Textures.com are provided under the Creative Commons CC0 License.
This means you may use these assets…
You can find the full details about the license on the Creative Commons website.
I would also encourage you to read the yellow note on the welcome page if you plan to build a project that relies on CC0 Textures in a big way.
Can I use the assets in a commercial film/animation project?
Yes, this use case is covered by the Creative Commons CC0 License.
Can I include the assets into my video game and sell it?
Yes, this use case is covered by the Creative Commons CC0 License.
Can I redistribute the assets as part of a shader/texture/resource pack?
Yes, this use case is covered by the Creative Commons CC0 License.
May I modify your assets as part of a project?
Yes, this use case is covered by the Creative Commons CC0 License.
Do I have to give credit?
No, it's not strictly required but I would of course appreciate it!
Simply write something along the lines of:
Contains Assets from CC0Textures.com, licensed under the Creative Commons CC0 License.