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The creators of the license recommend that it is used “principally for works whose purpose is instruction or reference.” Its most prominent user is Wikipedia.
The GFDL is only considered conformant if you
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Copyright (c) [YEAR] [YOUR NAME]. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".