Here's the zip file: jinsync_0.25_alpha.zip (19 KB).
It has been barely tested on a MacBook Pro running OS X 10.4, with JRuby 0.92.
Installation:
1. Download and set up JRuby 0.92
(See JRuby Wiki.)
2. Get the icalendar RubyGem: gem install icalendar
3. Snatch the JARs from Google Data API Java Client Library
(Set the CLASSPATH or put JARs in $JRUBY_HOME/lib so JRuby can access the GData libraries.)
4. Run jruby.rb in a Terminal!
Merry Christmas and a Happy Q4 ^_^.