The Open Definition, first released by Open Knowledge in 2005, sets out under what conditions data and content is open. Both legal and technical compatibility is vital, and the Open Definition ensures that openly-licensed data can be combined successfully, avoiding a proliferation of licences and terms of use for open data leading to complexity and incompatibility. Today it is the main international standard for open data and open data licences, with an advisory council of senior open data practitioners and can be found at opendefinition.org. The Open Definition has influenced and steered other communities of practice in the open movement, including open access to publicly-funded research, open hardware, and more, as well as governments’ approach towards licences.

Source: ODH