The live feed URL is at https://apps.dominicmanley.com/dabbles/guc-ical/. You can subscribe to that URL in Google Calendar or Apple Calendar or whichever calendar app you use.
By default, the feed is configured to Australian cinema releases and Perth's timezone. You change the region and timezone by appending parameters to the end of the URL like this:
More instructions can be found on the project's Github page. GUC-iCal is open source for anyone that wishes to selfhost or modify the original code.
Why is it called GUC-iCal?
For legacy reasons. Originally GUC-iCal was written for Australian (only) cinema releases and sourced data from Greater Union Cinemas (which is where the "GUC" comes from). Yes that's right... I shouldn't be allowed to name things.