「CC-BY-SAは、フリーであり続けることを意図したフリー・コンテンツ（「コピーレフト」）のための一般的なライセンスとなっています。ここでいうコンテンツは、文章、画像、映像、そのほかウィキメディアに取り入れることができないようなものも、すべて含みます。（A software analogy is using a copyleft license that's not GPL-compatible – it makes your work an isolated island for no particular gain.）」
What is dual-licensing? How are you going to administer it?
It simply means that content will be available under both the GFDL and CC-BY-SA licenses simultaneously, unless it cannot be due to the import of CC-BY-SA-only materials. We have worked with FSF and others to try to implement dual-licensing in a way that requires relatively little administrative overhead (or editor or user overhead). The outline of this arrangement were spelled out in e-mail by Richard Stallman, who was mindful of the need to make the problems of dual-licensing manageable:
ALL contributors agree to the following:
Wikipedia can release their newly written text under both GFDL and CC-BY-SA in parallel. However, if they imported any external material that's available under CC-BY-SA and not under GFDL, Wikipedia is bound by that.
All old revisions are released under GFDL | CC-BY-SA.
All new revisions are released with this license statement:
This page is released under CC-BY-SA.
Depending on its editing history, it MAY also be available under the GFDL; see [link] for how to determine that.
Isn't dual-licensing a complicated solution to this situation?
We believe Richard has done well at outlining an appropriate implementation for dual-licensing -- we believe that this dual-licensing compromise should ideally allow both dual-licensing proponents and dual-licensing opponents to support the switch. We recognize that this compromise won't fully please everyone, but hope neither the pro-dual-licensing side nor its opponents will dig their feet in. Part of the reason to keep GFDL integrated in the way we are proposing here is precisely that the GFDL has been of unquestionable value for Wikipedia over the years. We recognize that FSF is going forward in its own efforts to revise and evolve the GFDL. If you help us move forward with this compromise, we can revisit the dual-licensing situation in a year or two together with the FSF and see if it still is needed.
It will be the obligation of re-users to validate whether an article includes CC-BY-SA-only changes -- dual licensing should not be a burden on editors. This is also not intended to be bidirectional, so merging in GFDL-only text will not be possible.
We also propose to continue to permit GFDL 1.2-only media uploads for the forseeable future, to address concerns regarding strong and weak copyleft, until such concerns are fully resolved to the satisfaction of community members. (For a discussion of "strong copyleft" versus "weak copyleft," see generally the Wikipedia entry on "Copyleft".)
How will re-users determine whether or not an article is available under GFDL?
The CC-BY-SA license requires attribution, so when third party content is imported under "CC-BY-SA-only", it will have to be noted who the author is and that it was released under CC-BY-SA, as part of the normal, existing procedures through which projects make note of such histories (we recommend the article footer or the version history). Re-users will have to consult this information to determine whether CC-BY-SA-only content has been imported. Our licensing guidelines will make that clear.
Is the idea to allow Wikipedia to export CC-BY-SA-licensed content? Or to allow increasing importing of CC-BY-SA-licensed content?
In a word, both. This proposal aims at least to allow both importing and exporting CC-BY-SA-licensed content. Some very large projects already have adopted CC-BY-SA as a standard license. One of our goals here is to enable Wikipedia content to fuel these other projects more easily, and for them to provide content to us as well. We think lowering the barriers between projects in this way (by migrating or relicensing Wikipedia content under a more user-friendly license) will allow all these projects to become much richer.
All that sounds good, but sometimes I wonder if this is somehow a plot against the Free Software Foundation by Creative Commons folks – I seem to recall reading on mailing lists that there's some distrust between these groups.
Our experience has been that nobody's been plotting against anybody, and that all the participants have been remarkably friendly and cooperative, with their "eyes on the prize" of developing greater interoperability and compatibility among free-culture projects. It is worth emphasizing that Creative Commons has tried to recognize the strong commitment to freedom by the Wikimedia community in three ways:
by publishing a Statement of Intent regarding the CC-BY-SA license to clarify the purpose and future of the license;
by directly engaging with our community on our mailing lists regarding these issues.
Why didn't the FSF just say "OK, the next GFDL is the same as CC-BY-SA?"
"Because, despite Wikimedia sites being by far the largest corpus of GFDL content, the FSF needed to keep important details of how the license works the same for its original audience: authors of software manuals. Plus, many software manuals use features of the GFDL that are not in CC-BY-SA, such as provisions for cover texts and 'invariant sections.'" -- David Gerard
If the GFDL is so difficult for editors and users, why was it adopted for Wikipedia in the first place?
At the time Wikipedia began, there had already been some experimentation with other attempts at free licenses (at Nupedia and elsewhere), but none of them had the successful track record of the GFDL. At the same time, the Creative Commons free licenses had not been developed (or at least not in their current form) yet. So GFDL at the time was the best option available. Now that GFDL has evolved, and CC-BY-SA is available, we have a better option available, and one that will provide more compatibility among free-culture projects.
Isn't this new migration clause "surprising" and therefore legally invalid?
We believe that the migration clause is consistent with the language used in the GFDL 1.2: "The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns." The use of the GFDL by Wikipedia has given rise to "new problems or concerns", which were addressed by giving a migration path to a license "similar in spirit" which is, however, simpler to use in the context in which we are currently using the GFDL. While the specific wording of CC-BY-SA is different from that of the GFDL, the freedoms it guarantees and preserves are identical, and thanks to the Statement of Intent by Creative Commons, are guaranteed to be protected in the long term. The Free Software Foundation is a responsible custodian of its licenses and has made this change to the FDL in full awareness of its implications.
Are such unilateral changes to a license legal in all jurisdictions where people may wish to re-use our content?
We believe that licensing updates that do not fundamentally alter the spirit of the license and that are permitted through the license itself are legally valid in all jurisdictions.
Which licensing is suggested for other wiki projects (presently under GFDL, too) for the best interchange with WMF projects?
There are two paths here. One path would be for a wiki project currently under GFDL to take advantage of the new GFDL version (within the specified time period) and dual-license its content precisely as Wikipedia will dual-license its own content. Another path would be simply to license (or relicense) one's wiki under CC-BY-SA 3.x or later.
And for the transition period? ("Transition period" is the time from publishing GFDL 1.3 up to adoption of dual licensing policy at Wikimedia projects.)
To be prepared for any outcome of the community consultation, dual-licensing is the safest solution.
GFDL 1.2 mediaの使用が許可されなくなる可能性はありますが、今すぐというわけではありません. However, this will only happen if CC-BY-SA is modified to make it more explicitly a "strong copyleft" license for embedded media, requiring the surrounding content to be licensed under CC-BY-SA. Currently both licenses are somewhat ambiguous in this regard.
"It is also worth pointing out that a literal interpretation of the attribution requirement of the GFDL requires complete duplication of the "history" section of the article with every derivative work (not just the author names -- the entire section). For an article with thousands of revisions, this is obviously highly onerous, but even with just a smaller number of revisions, it is a significant amount of text."
How will this onerous requirement be avoided using CC-BY-SA?
Will another party be designated (as in section 4(c)) for credit (i.e. WMF as sponsor institute)?
Will the contributor be asked to renounce their attribution rights while pressing the "submit" button?