Thanks David for your answer,
Sure I haven't considered that point of you about the "commercial" clause and it makes sense. To me, "commercial" only meant that the work could be sold without the author's consent, I didn't realized that it could interfere with a company selling Arduino boards while offering a printed manual as a plus to the product.
As you know, the text I'm working on was supposed to be a French textbook to help my students to migrate more easily to embedded computer programming and programming in general. The school I teach in has a very short history in Digital Arts and it is usually considered that electronics, interaction and, of course, programming have nothing to do there. In Belgium, Art schools were, historically speaking, places where only Fine Arts could have a place. In 2001, a official government text defined the "Art schools : next generation", approaching universities like in many other countries while introducing sciences and techniques in their cursus.
While translating the Arduino reference, I began to add concepts and pieces of information that were missing (to me) in order to have the textbook more coherent and at that moment, I realized that it would be an aid for other French speaking teachers, that's why I contacted you by email at the end of July and began to post on the forum about it.
About the licensing, at first I thought a GFDL would be fine but then I saw the CC BY-NC-SA 2.5 licensing and I switch to the same license in version 3.0. I wrote about keeping the NC clause because my main concern is that my work may be used to "recruit" people for different activities, organized by private associations, even persons. A workshop should not be free of charge of course : my salary comes from the public financing, and those who give the workshop must get a salary as well. But what I afraid of is that copies of my work could be sold at a price higher than the actual production cost, just to artificially increase the price asked.
On the CC website, NC is explained as "The licensor permits others to copy, distribute, display, and perform the work. In return, licensees may not use the work for commercial purposes — unless they get the licensor's permission". I don't mind if my work is used for a workshop, advertised and freely distributed with Arduino boards or used in other schools around the world, I finally started doing it for these reasons. But I would have liked to be asked before using the work in a commercial environment, know the price asked and eventually waive the restriction.
You know, since my brother and I started teaching, more than 10 years ago (15 for my bro), we have written many textbooks, all were restricted to schools and selected classes but in our little experience, we had a few cases of our work copied and used under another teacher's name. Of course it wasn't about money and the "BY" clause protects against these practices but we really disliked so-called colleagues to have better reports (and then more chances to get a job and consequently a better salary) with our work. Even thought we never refused to help a young colleague to start by giving him or her a copy of our work.
Now, I would understand if you and your team prefer keeping the CC BY-SA license and I won't stop working on my textbook and probably release it under the same license. I do not intend to fork your work or something, you now have the complete explanation why.
Best regards from Belgium and thanks again for the good work you're giving to the community!
Stephan