Open this page https://keenthemes.com/keen?page=github to register. Provide your GitHub username and a valid Keen purchase code from your ThemeForest account and receive our invitation to access to the Keen's private repositories. Once you accept the invitation you will be added as a collaborator with following privileges:
You can use Sourcetree for free or any other Git client software to clone from the Keen's repositories:
https://github.com/KeenthemesHub/Keen.git
If the cloning was successful, a new sub-directory appears on your local drive. This directory has the same name as the repository that you cloned.