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.
Jeremy Estrellado shared a free visual breakdown image of how he created his Cobblestone Substance. The breakdown also features notes for you to understand all the details.
It is worth noting that Jeremy used a custom Randomize Mask node by Sergey Danchenko.
You can find the breakdown along with other projects and support the artist here.