The Historic County Borders Project (UK)

No specific permission is required [to use or redistribute the data]. However, the Historic Counties Trust would appreciate an appropriate acknowledgement of the use of the data, along the lines of:

"This [project/mapping/website/publication etc.] made use of data provided by the Historic County Borders Project."

For web publications, this statement should contain a link to the Project web site, http://www.county-borders.co.uk.