Wikipedia:Comparison of GFDL and CC BY-SA

This is a comparison between the GNU Free Documentation License and the Creative Commons Attribution Share-Alike 3.0 license.

Similarities between the two licenses

• Copyleft – any changes/derivative works must be available under the same terms. However, the 2 licences are not compatible with each other, so GFDL text cannot be put inside a CC BY-SA document unless it is used under the fair use doctrine. Compare this to incompatibilities with the GPL and the CDDL as evident with the controversy involving cdrtools, like oil and water.
• Authors must be attributed
• All copyright notices and notices of licence must be preserved.

GFDL specific elements

• The GFDL can require front or back cover texts, and force people to preserve invariant sections. The GFDL also requires users to "Preserve any Warranty Disclaimers".
• The GFDL absolutely requires that distribution be accompanied by the full text of the license (much like its sister for software, the GPL)
• The GFDL is primarily intended for software documentation and literary works, though it has been adopted by many wiki sites around the world influenced by Wikipedia.

CC BY-SA related elements

• The CC BY-SA license is written more generically and has no absolute scope for what it is intended to be used for.
• Unlike the GFDL, you only have to indicate the license it is available under if possible, while attribution of the author/source must still be done as a bare minimum. Distribution of the full-text is not required, which removes the burden of the legal requirement to distribute the entire text when printing.
• There is a human readable "summary" of the license available which sums up the terms a bit more nicely. The GFDL has a preamble for such purposes. Neither is legally binding, except possibly as a guide to intent.
• Creative Commons licenses are much more well-known than the GFDL, so they are used more often. This can increase the amount of possible external text content that could be added in the future to Wikipedia.
• For those using the Creative Commons search engines, Wikipedia articles theoretically could show up more often in results.
• There are dozens of Creative Commons licenses, while there are only 3 versions of the GFDL. This could result in confusion with other Creative Commons licenses (some of which have very different legal effects). (Different opinion by different user: This is not a problem, because most people are aware that there are different Creative Commons licenses, and there is only one Creative Commons Attribution-ShareAlike (BY-SA) license).
• СС licenses have "ports" to different copyright laws around the world [1], while GFDL is more US specific. However, the US or unported version will probably be used.

Key issues

• The issue of full text license distribution. This is a reason why we encourage dual-licencing of photographs because the GFDL is mainly meant for documentation and text documents but not images. As noted in the GFDL's article, you'd need to print out the entire GFDL, just to use one image!
• The issue of who will be attributed under the new terms.