To subscribe to a password-protected RSS feed in Radio UserLand or NetNewsWire, use the following format for the RSS URL:
For example, if the RSS feed is here:
...and your username/password is firstname.lastname@example.org, and xYz, then use this URL to subscribe to the feed:
Note that the '@' character in the username must be replaced with %40 (the URL-encoding for the '@' character). This is important for Manila sites, since members use their email addresses as their logins, and email addresses contain '@' characters.
Make sure that when using this URL format, that you replace the '@' character in your email address with %40.
I hope this helps everyone that has been asking for this feature.