You can easily invite guests to your presentation even if they don't have an InsiteVR account. Guests will only be able to view your InsiteVR project while a presentation is in session.
To invite someone first start a presentation. Then in the presentation menu click "Invite".
Copy the URL that is shown and send it to your guest.
When they receive the link they can click it to access your project. If a presentation isn't in session they will see a waiting screen until a presentation starts. Otherwise, they'll be able to join you in a virtual presentation right away!