Oskar Sigvardsson schreef:
You're missing my point. When you contribute to an already existing article, you are making a derivative work based on that article, which is licensed under the GFDL. The GFDL states that if you make a derivative work from it you have to license it under the same terms, you can't just PD that thing because you are using the original authors work and he didn't allow you to do that.
That's correct. At the same time, if the contribution can stand alone as a separate work, underived from the existing article, you may also license that separate work under any license you want; after all, you, the contributor, still have the copyright.
So: if you add a new paragraph to an article, there is a large chance that you can license it CC-SA (for example). Adding one sentence to an article in the middle of a paragraph, probably not. Changing one word: certainly not. (Reverting to an older version you didn't write yourself: no discussion possible)
But it's only the text of that one contribution that is dual-licensed.
If the article is CC-licensed as a whole (because all edits are from dual-licensing editors), there is no problem, and the whole article can be considered to be CC-licensed.
Dual-licensing notices should therefore say something like: "Unless derived from just-GFDL-licensed content, my contributions are ... etc", and people should check the article history before concluding anything about the licenses. Which makes multi-licensing much less usefull.
Eugene