By default, new organizations are configured to disallow the forking of private repositories.
If you allow forking of private repositories at the organization level, you can also configure the ability to fork a specific private repository. For more information, see "Managing the forking policy for your repository."
- In the top right corner of GitHub.com, click your profile photo, then click Your organizations.
- Next to the organization, click Settings.
- Under "Access", click Member privileges.
- Under "Repository forking", select Allow forking of private repositories.
- Click Save.