Article version: GitHub.com
Managing the forking policy for your repository
You can allow or prevent the forking of a specific private or internal repository owned by an organization.
People with admin permissions for a repository can manage the forking policy for the repository.
An organization owner must allow forks of private and internal repositories on the organization level before you can allow or disallow forks for a specific repository. For more information, see "Managing the forking policy for your organization."
Note: Internal repositories are available for organizations that are part of an enterprise account. For more information, see "About repository visibility."
On GitHub, navigate to the main page of the repository.
Under your repository name, click Settings.
Under "Features", select Allow forking.