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GNU Free Documentation License
The GNU Free Documentation License (GFDL) is a free license originated by the Free Software Foundation which permits a work to be copied, modified, and redistributed.
It is almost identical in intent to the Creative Commons Attribution ShareAlike license, although the two licenses are not technically compatible.
Key principles of the GFDL:
- Allows reuse and modification by anyone
- Allows use for any purpose, including commercial use.
- Requires attribution
- Derivative "descendents" of the work must also be covered by the GFDL. (Equivalent to the ShareAlike clause in Creative Commons license.)
- Requires a full copy of the license to be included with any copies or derivations. (This makes use on physical objects impractical - e.g. using a GDFL image on a coffee cup - and is one of the key difference with the Creative Commons Attribution ShareAlike license.)
Notes and references
- In practice, commercial use is greatly reduced as most commercial enterprises prefer not to have to release their modified versions for public use. Where commercial enterprises do reuse, under the GFDL or any ShareAlike license, their modifications must also be released under the same license, thus avoiding the problem of "exploitation" without contributing.
- GNU Free Documentation License, current version, (HTML with links to other formats).