Why CC-BY-NC-SA license?

[SamB]

Specifically, why NC? That's not considered a free/open license (it fails the first criterion of the Debian Free Software Guidelines and the Open Source Definition).

Is it actually a problem if people offer to sell printed copies of the website?

Looking at https://github.com/mu-editor/mu-editor.github.io/graphs/contributors, it seems like it might actually be possible to get people to agree to switch to CC-BY-SA (which lets people sell stuff, but doesn't let them "sell out" and take the material proprietary). (Since your actual software seems to be GPL'd, I'm guessing you wouldn't want to go all the way to CC-BY, which totally does allow taking material proprietary.)