Open Definition (OKF)
The Open Definition sets out principles that define “openness” in relation to data and content. It makes precise the meaning of “open” in the terms “open data” and “open content” and thereby ensures interoperability between different pools of open material. It can be summed up in the statement that: “A piece of data or content is open if anyone is free to use, reuse, and redistribute it — subject only, at most, to the requirement to attribute and/or share-alike.” – See more at: http://opendefinition.org/#sthash.fdlPmR68.dpuf
Open Definition | Open Definition.
(The OSD refers to Open Software Definition)