From their site: CKAN is the Comprehensive Knowledge Archive Network, a registry of open knowledge packages and projects. CKAN is the place to search for open knowledge resources as well as register your own. CKAN has a wiki-like interface that lets anyone add and correct packages. Examples of existing entries include a set of Shakespeare's works, a global population density database, the voting records of UK MPs, or 30 years of US patents. Those familiar with freshmeat, CPAN or PyPI can think of CKAN as providing an analogous service for open knowledge. CKAN is developed and maintained by the Open Knowledge Foundation.
The following is a list of historical changes that were made to this asset. Typically, once an API is published on ProgrammableWeb.com, the data we keep about that asset gets updated over the course of its life. For example, the endpoint or home page of the documentation might change. As a means of enforcing the integrity of our data, every time a non-trivial change is made to the data we keep about an asset, we require the entry of some changelog text before that change can be saved. This way, we have a great audit trail of all activity surrounding the asset. For each asset, the changelogs begins with the moment an asset is approved for publication on ProgrammableWeb. If you spot an error in our data and believe that a record needs to be updated in some way, the ProgrammableWeb team would very much like to hear from you at email@example.com