Build 0.17 is up, featuring multi-calendar support!
Note that the app will connect to download your calendar list at startup now. I'll fix that soon. Also, you cannot currently control which calendars are downloaded, you just get them all.
UPDATE: with build .172 Gcal Mobile no longer asks to connect to download your calendar list at startup; it only downloads your list when you perform an operation that requires synchronization with the Google Calendar Server. Also note that it now looks two weeks into the future. Some UI has changed a little (progress bars).
NOTE: With release .172, the .jar name has changed to GcalMobile.jar. You will have to uninstall the old version manually and reenter your account info.