An outside collaborator is a person who is not a member of your organization, but has access to one or more of your organization's repositories. You can choose the level of access to grant for each outside collaborator. When you add an outside collaborator to a repository, you'll also need to add them to any forks of the repository you'd like them to access.
Adding an outside collaborator to a private repository will use one of your paid licenses. For more information, see "About billing for your enterprise."
An organization owner can restrict the ability to invite collaborators. For more information, see "Setting permissions for adding outside collaborators."
Before you can add someone as an outside collaborator on a repository, the person must have a personal account on your GitHub Enterprise Server instance. If your enterprise uses an external authentication system such as SAML or LDAP, the person you want to add must sign in through that system to create an account. If the person does not have access to the authentication system and built-in authentication is enabled for your enterprise, a site administrator can create an account for the person. For more information, see "Configuring built-in authentication."
If your organization requires two-factor authentication, all outside collaborators must enable two-factor authentication before accepting your invitation to collaborate on a repository. For more information, see "Requiring two-factor authentication in your organization."
You can give outside collaborators access to a repository in your repository settings. For more information, see "Managing teams and people with access to your repository."