Open Government Licence
The Open Government Licence (OGL) (Wikipedia) is a copyright licence for Crown Copyright works published by the UK government. Other UK public sector bodies may apply it to their publications. It was developed and is maintained by The National Archives. It is compatible with the Creative Commons Attribution (CC-BY) licence.
Using OGL data in OSM
Whilst the OGL states that data may be reused, it does not guarantee it. Datasets should be reviewed on a case-by-case basis.