The Open Definition
The Open Definition (formerly Open Knowledge Definition) is published by the Open Knowledge Foundation (OKF) to define openness for any type of data, content, or other knowledge. The definition's stated purpose is to "[make] precise the meaning of ‘open’ with respect to knowledge". Although it draws philosophically from both the open-source and free software movements, the Open Definition prioritizes license compatibility over copyleft principles requiring derivative works to be released under a free license. The Open Definition contains requirements for content licenses to be considered open licenses, and the OKF maintains a list of compatible licenses. The definition also requires open access, machine readability, and the use of open formats. The OKF's Open Software Service Definition is derived from the Open Definition.