Hello,
In order to subscribe to the calendar publicly, you have to sign in. Many calendar apps including Apple's do not have the ability to sign into calendars to subscribe.
Seeing as calendars are not exactly sensitive information, may I suggest allowing access to /dvr/jobs/calendar.ics WITHOUT authentication.
Essentially, I want to be able to access http://***.u.channelsdvr.net:8089/dvr/jobs/calendar.ics without having to sign in, so that calendar apps can subscribe and update while I am not home.