Once you open up your course to guests, anyone on the Internet can access it without the need of an account on the system.  It is possible to set an optional password for guests.

To enable guest access:

• Go to the Participants (left menu) → Gear Icon → Enrollment Methods
• If Guest access is not already listed, select Add Method → Guest Access.  
• If Guest Access is listed, click on the gear icon to modify the settings.
• Turn on guest access and optionally set a password.