Yes you can run Aperture under JRuby.  I am using 0.9.8 and I just upgraded to 0.9.9.  It is very easy to use the Java libraries from within JRuby (and I am using Ruby on Rails for the UI) and vice versa.  Follow the wiki located here:

http://www.headius.com/jrubywiki/index.php/Calling_Java_from_JRuby

 

Kevin