The current ruby bindings do not work on JRuby do to the use of mkmf in the build. It used to be that on jruby, the build would just skip over the extconf.rb step and only install the pure ruby code. (See the current version up on <http://github.com/fauna/thrift>.
I've been fighting with rubygems to figure out why I can't make this work like I was able to with 0.2. Unfortunately, I'm at my limit, so here's just the bug. Help appreciated.