Oh, of course, you're absolutely free to use it to create professional content! I only insist that you tell me about it and show it to me!!!
As for coding, believe it or not, I approach everything in a similar fashion, growing things "organically" so to speak. This way I know I will break forward rather than getting stuck on trying to realize elaborate concepts. Every time I raise "dimensions" of complexity, though, I do revisit the whole code and defragment it, one might say. Here and there comes a point when I have figured out a great deal of new techniques, and then I might rewrite whole sections or even the very foundation. So, yeah, I am growing my code, keeping active and allowing it to evolve. This way I can respond to revelations along the way, which I otherwise might not have had, for example. There also comes a fair share of happy accidents, which invite their own branches. Funny enough, the "brush image" section is such a byproduct. Initially I wanted to write a more sophisticated way to blit images on an irregular quad polygon. As you know, GL will create two triangles with their own UV mapping and then just strap an image onto those, creating obvious splits between the two triangles, if they are deformed. So I wrote a shader that recomputes the uvmap across a quad. To test it I would make a square from which to read an image and an irregular quad somewhere else. And then I realized...hey, this could be fantastic for brush images! It's also perfect for remapping in perspective, which is something I will finish up and some point, too.
BUT we're derailing this thread, haha....
... so, yeah, I'm super happy about everything you've written up there and if you wish to, you can totally start a little OFF TOPIC thread regarding your game or anything else, for that matter! And don't hold back to start your own gallery thread here, too, of course!
OH, besides, I used Verve to do textures with displacement for some 3d projects in the past! Quite nice for that, too. That's why I made the component export.