To allow clients, contractors and external team members to view projects, you can add them as Project Members with "View Only" capabilities.
Starting from Projects > Project Name > View Team > Add Team Member > Enter Team Member email and select permission level > Invite.
Your new Team Member has been sent an email. If they already have an InsiteVR account they will click accept in the invite and be added to the Project. If they do not have an InsiteVR account they will be prompted to make one and then be added to the Project.