FDL

FDL is an acronym that can refer to several different things, but it is most widely associated with the Free Documentation License, commonly called the GNU Free Documentation License (GFDL). The GFDL was created by the Free Software Foundation to ensure that manuals, textbooks, and other documentation could be freely copied, modified, and redistributed.

The license is designed to preserve freedom for downstream users by requiring that redistributed copies carry the same license and retain attribution to authors. It includes provisions about license notices, source document availability, and, in some versions, invariant sections and front-cover or back-cover texts. These features have been a point of contention, influencing how compatible the license is with other licensing schemes and how it affects derivative works.

Versions of the GFDL have evolved since its introduction, with version 1.3 being a notable update intended to address criticisms and improve compatibility with other licenses. Over time, many projects moved toward more permissive or widely compatible licenses for new content, and some large projects avoided new material under the GFDL in favor of other licensing options. Nevertheless, the GFDL remains part of the history of open documentation and continues to apply to older content that was released under it.

Beyond the Free Documentation License, FDL can stand for unrelated terms or organizations in different contexts. When encountered, the exact meaning typically depends on the surrounding subject matter or field.