Everyone in SpecFuse is grouped into an organization. When a signs up for a trial they create and name an organization in the process. They then become an organization admin.
Additional users can be invited to SpecFuse by an organization admin.
Once users join, they can then be added to projects. Users can only ever see and access the projects they are specifically added to.
Project admins can add additional users to their project via the Admin view. Users will receive a notification once they have been added, letting them know they can now access the new project.