Great find, thanks!
I found something similar (the fact that there are differences is somewhat worrying) via:
(yes, it is available... in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying 'Beware of the Leopard'. ;) )
I guess the first thing I needed to do was realize I needed the API documentation :) I didn't consider creating a skin "application programming".
Both documents seem very similar in graphic design and document structure, but there are many differences in content. e.g. given the first 4 namespaces (in alphabetical order) both contain the DotNetNuke.Application and DotNetNuke.Common namespaces, but the website contains DotNetNuke.Authentication.LiveID and DotNetNuke.Authentication.OpenID namespaces which the helpfile does not, while the helpfile contains DotNetNuke.Collections and DotNetNuke.Collections.Internal namespaces, which the website does not.
Both document lack a document title and introduction, so it's unclear to me what the intended purpose or target audience of each is.