I’ve been a big fan of calcurse since I first installed it. Frederic Culot, its author, has written that the latest version now can import ical files.
…[S]ince last calcurse version (2.3) which was released last week, it is now possible to import ical files. The sync capabilities related problems mentioned in the above comments should be fixed now, as calcurse is now able to import / export ical files.
This means users can now use calcurse about as seamlessly as any other calendar application, but without all the bloat and slowness that makes them a nuisance to use. Visit the download page for sources and availability for various distros and BSDs.