Google Calendar Sync

because for one thing it's closed source so we can't modify it, and I believe it goes with Outlook, which cannot be portable so it basically demeans the portability. Maybe try downloading the calendar in google as a sunbird format and have sunbird instead?

There is OutlookGoogleSync, but it is one-way only (Outlook --> Google).

Web site is: http://outlookgooglesync.codeplex.com/

SyncDocs can be installed as a portable app, but you still need to pay to unlock the full version, so it can't be packaged as a PortableApp.

http://www.syncdocs.com/