Licensing TN: better address the license compatibility issues

[jouvin]

In the first version of the TN, there is no explicit paragraph on license compatibility issues. @valassi provided a first draft for such a paragraph in #8. @sextonkennedy also suggested in #4 (#4 (comment)) that we add a reference to:
https://en.wikipedia.org/wiki/GPL_linking_exception
as this clause has some relevance for our case since many of us use a framework where dynamic loading of libraries is a core strategy in forming our large applications.

This TN revision should also address @valassi comment in #4 (depending of whether #8 is merged or not).