The UK Government’s Information Asset Register (IAR) managed by OPSI (Office of Public Sector Information). From the website:
The IAR lists information resources held by the UK Government, concentrating on unpublished resources. In doing so it enables users to identify, from one single source, the information held in a wide variety of government departments, agencies and other organisations. inforoute is a key part of the Government’s agenda for freeing up access to official information.
As of 2007-08-09 at least 111k items in the register.
Access: Not fully open. Access via a web form query interface but no database dump or automated way of getting access to the information.
License: No license specified. Note that here the information at issue is the metadata in the register not the actual items referred to by the register.