Demo can mean 1 of 2 things. Either they have not activated the account from the link sent to them when they signed up. Or their account was deactivated by setting it back to Demo which is very limited access. No posts or message abilities, but able to login.

Free allows 5 posts and 5 private messages per day.

Premium is unlimited access to the site and is no charge although people seem to be confused about that most of the time thinking they need to pay to upgrade. Maybe I need to make some changes because back in the day I was going to charge a very low monthly fee, but decided against it and take a different approach.

You're not a bother. Hope this helps!