Joshua Gay's edit looks sloppy at best: I found at least 2 clauses and a section in http://creativecommons.org/licenses/by/4.0/legalcode that look incompatible with any GPL. I've written a letter to the FSF asking them to clarify this matter and the properties of the edit. This is what I just got in reply, from none other than Joshua himself (nested blocks are his quotes from my letter): > Hello, > Thank you for writing. > > * It doesn't mark the license as "compatible with the GNU GPL or FDL" > > with the left-side line. > > The color doesn't specify a version number of the GPL. I have been > waiting for confirmation from our general counsel that CC BY is > incompatible with GPLv2 and the FDL before updating the color on the > left hand side. Hopefully that will be soon. > > > * It doesn't comment on this decision as if it's something obvious. > > Which it is not: > > * The http://creativecommons.org/licenses/by/4.0/legalcode#s3a3 > > restriction looks drastically incompatible > > First note that both licenses make use of words like reasonable and > within reason. Interpretation should be done with that in mind. Here is > our position on this as I understand it. You are right that we should > have a more formal statement and I will try to get one prepared that > we publish on the site. > > GPLv3 7(b) states that you can add terms "Requiring preservation of > specified reasonable legal notices or author attributions in that > material or in the Appropriate Legal Notices displayed by works > containing it;" > > The FSF interprets this as to include a licensor doing something such > as removing certain parts of the reasonable legal notices or marking > them in ways as different from the original. > > > * http://creativecommons.org/licenses/by/4.0/legalcode#s4 grants a > > set of rights whose relation to those granted by the GPLv3 is very unclear > > How are they unclear? I do not see what is unclear. > > > * http://creativecommons.org/licenses/by/4.0/legalcode#s2a5B > > appears to forbid relicensing which is a requirement for GPLv3 compatibility as per > > http://www.gnu.org/licenses/gpl-faq.html#WhatDoesCompatMean > > A person does not need to relicense a work to create a combined work > with the GPL. A CC BY licensed work that is incorporated into a GPL > licensed work would retain a copy of the CC BY license and all CC BY > notices. One would simply add to the work as a whole and in relevant > plces notices about the GPL and a copy of the GPL. > > CC BY does not restrict adding additional terms so long as those > additional terms do not restrict "exercise of the Licensed Rights by > any recipient of the Licensed Material." > > I will see about adding these clarifications somewhere. > Thanks again for emailing us. > > Joshua Gay > Licensing & Compliance Manager > Free Software Foundation This is the reply I got on further clarification of CC#s3a3. He believes it's compatible by doing a narrow interpretation: > > The incompatibility as it appears to me is that GPL gives no right to > > change any terms > > for a licensee who has already received a license (or receives it from > > an older copy) - > > since a license is irrevocable and is granted on the terms that > > accompany a specific copy. > > > > So, your interpretation of this CC clause is that it only applies > > to the moment one receives a copy from the copyright holder, not to > > any later moment > > or receiving it from any other party? > > That is my current understanding. Do I have a reason to think it would > mean at a later date? I assumed such a request would need to be made > alongside the license itself. I will ask Creative Commons what their > interpretation is. > > I am not a lawyer and I have no ideas how courts would interpret this. > But, I'm not sure how one could reasonable expect a work to be put > into the wild, modified and remixed for a period of 75 or 80 years and > then it be reasonable that a licensor could come along and ask for all > of those notices to be removed. And here's the final update, right from the horse's mouth. **The "reference removal" CC clause *is* an obstacle to declaring CC-anything-GPL compatibility. Whatever the final result would be, *as of now*, they're deemed incompatible.** > > I suspect the clause does have such a use in mind. Its intended use > > appears to be the case where a copyright holder sees their work used > > in > > a context that they deem inappropriate - so they wish any reference to > > them > > removed so that their perceived reputation doesn't suffer. > > Creative Commons sent me a clarification and it is the case that the > intent of the license is so that a user could ask after the fact. > *However*, they explained that "to the extent reasonably practicable" gives a person a lot of flexibility in being able to simply deny the > request of the original licensor. I am interested in finding out some > other legal opinions on how strong the language "to the extent > reasonably practicable". Like how easy it is to make that argument as > a licensee. I believe this is will be the next question in the public > discussion mailing list. I will also open up an internal discussion at > the FSF and with our lawyers to make sure they think the language > "reasonably practicable" is sufficiently strong. Why he made the edit when he did? Perhaps, because that's when he checked the compatibility. He [actively participates in the CC-BY-SA - GPLv3 compatibility effort][1] - that could very well be the reason that drew his attention to that matter. The "transitive" compatibility of the earlier versions of the CC-BY has already been well explained by apsillers in [c556709][2]: Earlier licenses are incompatible *on their own* but are compatible if the work's license *allows relicensing to a compatible version.* As you can see, this is a general principle not specific to a license. [1]: http://lists.ibiblio.org/pipermail/cc-licenses/2015-February/thread.html [2]: http://programmers.stackexchange.com/questions/272335/how-and-when-had-the-cc-by-license-become-gnu-gpl-compatible#comment556709_272335