The superuser account is used as a backdoor in case you get locked out you shouldn't be using it otherwise..
If you want anonymous access you need to create a limited user (using an asterisk (*) as the username and password - this tells Tvheadend to accept any value) and then create yourself an admin account.
Note: be careful when picking options for the wildcard (*) account as whatever you pick will also apply to other accounts..
If you give Admin access to the wildcard account and create another user they will also have access to the Admin/Configuration tab even if you've not given them access/enabled it.
This is because Tvheadend by default combines the options of the wildcard account with other accounts as * matches anything.
HTH..