UK Crown Copyright open licence. Permissive attribution-only for UK government information.
The Open Government Licence (UK) is the licence under which most UK Crown Copyright material is made available. Version 3.0 (2014) is a permissive attribution-only licence, intentionally drafted to be compatible with Creative Commons Attribution 4.0 and the Open Data Commons Attribution Licence.
OGL-UK was the first widely-deployed national open-government licence and became the model that several other Commonwealth governments adapted, including the Canadian, New Zealand, and Australian variants. The compatibility-with-CC BY drafting was deliberate — it allowed UK government data to be combined with international open-data sources without licence-friction.