Open knowledge is knowledge that one is free to use, reuse, and redistribute it without legal, social or technological restriction. Open knowledge is a set of principles and methodologies related to the production and distribution of knowledge works in an open manner. Knowledge is interpreted broadly to include data, content and general information.
The concept is related to open source and the Open Knowledge Definition is directly derived from the Open Source Definition. Open knowledge can be seen as being a superset of open data, open content and libre open access with the aim of highlighting the commonalities between these different groups.
Similarly to other 'open' concepts such as open data and open content, though the term is rather new, the concept is old. For example, one of the earliest printed texts of which we have record is a copy of the Buddhist Diamond sutra produced in China around 868AD, and in it can be found the dedication: "for universal free distribution".
Organisations and activities promoting open knowledge 
- Alliance for Taxpayer Access (ATA)
- Enabling Open Scholarship (EOS)
- Open Knowledge Foundation (http://www.okfn.org/)
- Open Source Geodata
- Science Commons
- SPARC (Scholarly Publishing and Academic Resources Coalition)
See also 
- Libre knowledge
- Comparison of open-access journals
- Knowledge commons
- Definition of Free Cultural Works
- Open access (publishing)
- Open content
- Open data
- Open Knowledge Network
- Open source
- Open Access Directory
- Business Intelligence 2.0 (BI 2.0)