Bookdown is a commonly used package for authoring reports, books etc. in the R language (but can just be used for writing anything, if you know Markdown, and you want a way to produce HTML, PDF, ePub etc. outputs automatically). The code itself it released under GPL3 (although not in a very "formal" way...)
That example is licensed CC-BY-NC-SA, and not GPL3.
Is this allowed, under the GPL3 terms? This Creative Commons website suggests not.
The underlying issue is that the "book" uses the CSS, JS and HTML code from the template (the "GitBook" template) in the BookDown package. I am new to all this, but from some Googling, this seems slightly a contentious area. There is no question about the PDF version of the book (actually, you can find arguments either way; here is an argument that the PDF is also covered by GPL3). But the website version seems to use "code":
A broader question here is: how do you separate the code from the content of a website? One could guess that in the example above, the intent was to license the content of the book as CC-BY-NC-SA.
I ask the same question, but now suppose I am using a website template which is licensed under CC-BY-NC-SA (a randomly chosen example -- sorry, this example is bad, as I'm not sure it has any real content; but in principle I hope you see the idea). Can I license my website content (but not the CSS, js etc. code) as CC-BY, for example? Or is the whole website a derivative work?