This is the second discussion prompt relating to one-way compatibility from BY-SA to the GPLv3. This email relates to license scope, with a particular focus on how the two licenses deal with patent rights.
As we all know, the tone and scope of the two licenses differ, due largely to the fact that the GPLv3 was designed for use with software and software-like works. Of course, both licenses are primarily designed to license copyright, but each license also covers some rights closely related to copyright, which means the scope of each varies slightly. GPL covers “copyright-like laws that apply to other kinds of works, such as semiconductor masks,” while BY-SA covers “Copyright and Similar Rights,” which is defined to include neighboring rights, sui generis database rights, and other closely-related rights.
The most significant difference in license scope is the treatment of patent rights. BY-SA expressly reserves patent rights to the licensor, while GPLv3 expressly includes a patent grant from each contributor.
Because patent rights are expressly excluded from BY-SA, there is no reliable claim of an implied license to do things with a BY-SA licensed work that implicate patent rights. From a compatibility perspective, this means that when a BY-SA work is adapted into a GPL-licensed project, downstream users of the project would not have patent rights to the BY-SA work. (Although the GPL includes a patent license, the scope of rights licensed by the BY-SA licensor cannot be expanded because an adapter applies the GPL, just as it is not expanded when an adapter applies a later version of BY-SA that licenses more rights than the original.)
This problem is largely academic, given how rarely BY-SA works are subject to patents that would be implicated by simply reproducing or adapting the content. (In fact, CC has not yet been able to come up with a realistic use case, but we welcome concrete examples of those from our community that we may be overlooking.) Nonetheless, as a theoretical matter, it creates a problem because it is possible to imagine a downstream user of a GPL project mistakenly assuming she does not have to worry about patent rights even though a BY-SA work is adapted into the project.
We have asked the FSF to weigh in on this issue. We are also curious what all of you think. Does the unlikely but serious risk of patent problems for downstream users outweigh the benefits of compatibility? Can we do enough to alleviate this risk with proper education for reusers?
We look forward to your input.