You don't need to "put a copyright" on your work. As fas as I understand it (I'm from Germany, European laws are different from U.S. laws and IANAL) you don't need to do anything, If you write a text, create an image, write a program it's automatically protected if it's unique enough. So, no copyright for "Good Morning, everyone", but lengthy articles can qualify. But even if you have a copyright on your text, someone else may write a text which gives the same informations just with his own words, without violating your copyright.

With software (yes, I do code, started programming on a TRS-80 some aeons ago) it's the same. If there isn' a patented algorithm you may recreate any program you encounter, proved by the countless "Flappy Bird" clones in every App Store. If you see a shader and rebuild it you would not break any copyrights, IMHO. If you find a shader which basically consists of five nodes and a couple of values inside, then I would assume you are save to use it, since it's more a "Good Morning" instead of a work which qualifies for a copyright.

But look at things like BB's skin shaders, like his procedural chain mail. Those are complicated enough to qualify. Still, you may recreate the shader from scratch, but I don't see how a mathmatic source code differs from a python source code, and why complicated shaders with many, many nodes shouldn't be copyrightable.

There are copyrighted shaders for Blender's cycles, (see this link ) which to my knowledge aren't much different - just a (big) bunch of nodes. But since the shop puts a regular licence on it, I assume that they think that the shader is copyrighted.

For my understanding, it does not change much if you use source code or building blocks like nodes to generate a function, a program. And I fail to see what makes shaders different. Most of them are just far too simple to qualify for copyright, IMHO.

I am not a lawyer, probably I missed some important point. 

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

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