John,
Can you provide more details on which "calendar library" you are referring to?
The link you've highlighted in Google calendar points to a file in iCalendar format. You'll probably want an iCalendar parser to handle the file, I've personally used this one, but it doesn't handle everything in the spec:
https://github.com/luxifer/ical.
Depending on the parser that you choose it may have functionality to fetch a file by URL, but most likely you'll need to perform an HTTP request to that URL, read the body, and pass it to a parser.
- mingle