The CKAN code that runs this site is open-source and licensed under the GNU Affero GPL . It is hosted on KnowledgeForge, and the project home page is here: http://knowledgeforge.net/project/ckan/.
All material on this site is open and can be freely used, reused and redistributed. Formally, the data/database is licensed under the Open Data Commons Open Database License v1.0, with all copyrightable content in that database plus any additional content on this site licensed under a Creative Commons Attribution Share-Alike v3.0 license.
For convenience, all material - including all package, tag and revision information - is available in bulk, in the form of a full dump of the CKAN database. This (gzipped) dump file is updated daily and can be downloaded from http://www.ckan.net/dump/.