GNU Free Documentation License
Material licensed under the current version of the license can be used for any purpose, as long as the use meets certain conditions.
- 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.