We describe the Creative Commons (CC) licenses first, since they have various options, which are a convenient way to compartmentalize and describe the features of other open licenses. They are known by abbreviations, so a license might be shortened to something like just CC BY-SA.
Source versus Output
Creative Commons licenses are designed for a variety of media, and so are very popular. For example, images are often licensed with a Creative Commons license.
However, consider the case of a document distributed as a PDF which has been created from source, such as PreTeXt or LaTeX or Markdown. An author may put a CC BY-SA license on the PDF while retaining traditional copyright on the source file(s). While the license allows modification, how practical is it to modify a PDF? Worse, we have seen this situation for projects described as “open source.” This explains our use sometimes of the term “openly licensed content.”
If you are serious about your project being open source, and you want to send that signal to your readers, then mark your output with a CC license and mark your source files as also having the same CC license. This is usually accomplished by a statement at the top of each source file asserting copyright and then stating the license. Or this statement can point to a top-level text file, often named COPYING or LICENSE, with more precise license information. See the PreTeXt distribution for examples using the GPL software license.
It is natural to consider that you have devoted considerable time and effort to your project, and with an open license you will now be donating it to the world to read for free. So you might think, “Why should somebody else profit?” Thus, the NC option is alluring. But think about it for a minute.
Suppose a commercial publisher hires an experienced copy editor to go through your book, correcting errors and tightening the prose. Then the publisher prints the improved version of your book in a nice hardback version, and sells the book for $250. If you simply put the BY-SA options on your license, that publisher is obligated to (a) give you credit for authoring the original version of the book, and (b) make the copy-edited version available again with a CC BY-SA license. Now there is a business opportunity for anybody in the world: make a print-on-demand version of the copy-edited version, and sell it for $200. Then it is a race to the bottom. Eventually the price will come down to the cost of manufacturing, plus some small compensation for managing the relationship with a print-on-demand service Chapter 12. Just how much profit potential is there really available for others?
We assume you have written a book because you have something to say, and chosen an open license because you want to be read. If you do place an NC option on your CC license, then you have made it impossible for anybody else to help you distribute your book in physical forms. A CC BY-SA license already makes your work unattractive to a commercial publisher who wants to charge an unreasonable price, and adding an NC clause simply chokes off some distribution options, limiting the reach of your work.
Will your monograph on the reptiles of the Mongolian steppes ever become a screenplay? As exciting as the topic is to you, we think Hollywood feels otherwise. An ND option probably makes little sense for scholarly works. An conversely, if you get hit by a pie truck tomorrow, it will be a lot easier for an enthusiastic reader to take over custody and maintenance of your project, and they will be required to continue with the same license if you have employed the SA option.
for a CC license with the Attribution and Share-Alike options. If it was not obvious already, this is our recommendation for scholarly work if you choose to use a Creative Commons license. This is an example of what is known as a copyleft license.