Codespaces have been constrained to specific users or all members of an organization, which, while great for day-to-day software development, didn't allow everyone in an organization to participate. That's why we're so happy to announce that as of today, you can invite outside collaborators to access Codespaces.
Outside collaborators expand Codespaces to use cases like interviewing, training, and teaching, where you can easily add outside collaborators to specific repositories within your organization (or in certain cases, giving each collaborator their own repository). Start by granting "All members and outside collaborators" access to Codespaces, then inviting collaborators to repositories you want them to use Codespaces in.
For more information, see "Enabling Codespaces for your organization."