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The GNU FDL License can be attributed to manuals, textbooks, or other functional and useful documents to make them freely available in the sense of freedom to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. The license also preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
Mostly historical reasons made OSGeo choose to copyright the content of this Wiki and the OSGeo web site under the Creative Commons Attribution-ShareAlike license.
Applying the GNU FDL license to educational material is one method of producing Appropriately Licensed Material for OSGeo.