Correct. But my doubts are over the output of the software.
On one hand, the output depends on your artistic instructions, so you are entitled to it. On the other hand, the tool greatly restricts the solution space, so the tool itself (and consequently its author) has artistic merit over the result.
I think a simple way to explain the MIT license is that you can do whatever you want with it as long as you don't say that you created the library yourself.
Textures that you create are as yours are images you create in Photoshop. Probably even more yours than that ;)
My doubt is about authorship. If I make a texture with texgen, can I claim to be the author? Probably yes, but where do we draw the line? If I create a Minecraft world by selecting a single seed, and take a slice of the world as a 2D image, can I claim authorship? What if I didn't even change the seed, just pressed "create"?
I think it depends on the country, but thinking about authorship over procedural generators is weird.
As an example: if I use a seed to create a grainy texture, it probably isn't original. If I use the same image as a grain filter for a photograph, the result may be original (in a legal sense). Both operations are trivial and just a click of a button (or two), so I think the discussion about the ease is moot in that context.
I couldn't claim authorship of a machine generated work. I would feel better about claiming authorship of something I've spent a while working on and finding combinations until I get something I like.
Do you claim authorship of Photoshop's cloud filter?
It's a slightly worrying grey area. If a generator only has 2 possible combinations of all its various settings, claiming authorship of the output is clearly absurd. If it has 16 trillion possible combinations, maybe less so.
Where do you draw the line? If people can copyright a bunch of settings, does that prevent people from using the generator with randomized parameters in case they accidentally hit a lawsuit?
On one hand, the output depends on your artistic instructions, so you are entitled to it. On the other hand, the tool greatly restricts the solution space, so the tool itself (and consequently its author) has artistic merit over the result.