Use this neat little CGI to convert ICAL files, for example exported from Google Calendar, to VCAL version 1 files, that can be for example imported into the Palm Desktop 4.x software. In other words, use this to import Google Calendars into Palm Desktop, okay? For more info, go to http://cpbotha.net/2007/04/26/google-calendar-to-palm-desktop-conversion/. Please leave a comment on the linked blog post if you use this CGI, even if it doesn't work.
Click the "Browse" button to select an ICS file on your side, then click on the "Convert to VCAL" button to convert to a VCS file. You'll get a VCS file that you should import into Palm Desktop with File | Import.
Oh by the way, you use this script ENTIRELY AT YOUR OWN RISK. :)