hi, I was read this faq:
“Can I create official documentation and textbooks?
Yes. We’d love to hear about any contributions you’d like to make. Please utilize our resources and share information with the community. You can kick off discussions about this on the forums, chat with us on Twitter, add to the Wiki and attend our weekly Twitch stream.”
It say that I can use their resources, but not sure if i can sell it if i include a figure they created in my textbook.