Any class or library in VBScript or asp classic that I can use to parse RRULE (iCalendar - RFC 5545) and generate a list of Upcoming Events?
you can try with rrule.js , is a javascript library , If you send RRULE string like
FREQ=DAILY;DTSTART=20150409T030000Z;UNTIL=20150511T025900Z;WKST=MO;BYDAY=MO,WE,FR
the library show a grid with all recurring events.