Documentation license comparison

Contents 1 Preamble 2 FDL overview 3 CC by-sa overview 4 Incompatibilities 5 Comparison 5.1 Relationship with code 5.2 Collaborative documentation 5.3 Printed documentation 5.4 Existing documentation 6 Conclusion

Preamble

The Maemo developer guide is licensed under the GNU Free Documentation License (FDL), while the Meego wiki and Maemo wiki content is licensed under Creative Commons by-sa (CC by-sa).

This is an issue, because the licenses are incompatible, and we will thus be unable to copy (relevant) pieces of the Maemo developer guide to avoid building from scratch and leverage existing content. It would be preferable to have the Meego developer guide and Maemo developer guide be licenced under the same license. This page compares the licenses from the point of view of technical documentation. Other documentation sources, such as Fedora's documentation, is licensed under CC by-sa 3.0.

FDL overview

The GNU Free Documentation License was designed to allow documentation to be reused for any purpose, on condition that anyone could do the same thing with the resulting derivative versions. In this sense, it is the documentation equivalent of the GNU GPL. The license has a number of conditions associated:

• All previous authors of the work must be attributed.
• All changes to the work must be logged.
• All derivative works must be licensed under the same license.
• The full text of the license, unmodified invariant sections as defined by the author if any, and any other added warranty disclaimers (such as a general disclaimer alerting readers that the document may not be accurate for example) and copyright notices from previous versions must be maintained.
• Technical measures such as DRM may not be used to control or obstruct distribution or editing of the document.

The provision for invariate sections makes the GPL and FDL incompatible in both directions, except for segments which fall under "fair use" (according to debian-legal, at least).

CC by-sa overview

Creative Commons by-sa allows modification and redistribution of documentation on condition that:

• Original authors' work is attributed
• Anyone redistributing derivative works must offer the work under the same terms

Creative Commons by-sa 2.0 is incompatible with the GNU GPL also.

Incompatibilities

The FDL and CC by-sa licences are incompatible, because:

• Invariant sections of documentation, as defined by the FDL, are incompatible with CC by-sa requirements
• Reproducing the entire text of the licence and changelog of previous changes (as required by FDL) is incompatible with CC by-sa

However, content licensed under CC by-sa was potentially compatible with FDL for a short period (between the release of FDL 1.3 in November 2008 and August 1st 2009) on condition that:

• Documents did not contain any invariate sections
• The documents were part of a massive multiauthor collaboration project (such as Wikipedia)

Comparison

Relationship with code

Both FDL and CC by-sa are incompatible with the GPL. To allow GPL or BSD licensed code samples to be included in documentation and reused under GPL or BSD by readers, an exception is required to either license.

Collaborative documentation

Either license is fine for collaborative documentation, but the requirement to reproduce a list of changes in print editions makes FDL more cumbersome for printed documentation.

Printed documentation

The requirement to ship the full text of the license and the list of changes makes FDL less attractive for printing shorter documents. For book-length documents, both FDL and CC by-sa have been used successfully.

Existing documentation

More documentation is licensed under CC by-sa than under FDL. Some examples include Fedora, Wikipedia and Moblin, and GNOME are also considering a license change for its documentation. The Maemo developer guide is licensed under FDL at the moment. If re-using existing documentation is a concern, then CC by-sa is a better choice.

Conclusion

Both CC by-sa and FDL have similar issues with including code samples. CC by-sa is more attractive for printed documentation and wikis.

Since there is a large mass of existing documentation licensed under CC by-sa, there is a good argument for having CC by-sa as the primary license.

To allow reuse of the Maemo developer guide, I recommend that the Maemo developer guide be relicensed to CC by-sa, or dual licensed to FDL and CC by-sa.