I'm one of the contributors to the API Copyleft License. Are you using it for a public project? I'd like to feature that kind of work on https://apicopyleft.com.
Keep reading! That is just the Purpose section, which summarizes the license. The specific sections affecting copyleft are Copyleft, Prototypes, Applications, and Contributing. I think they are slightly easier to read and understanding on the master branch of the development repository: https://github.com/kemitchell/api-copyleft-license/blob/mast...