Rucene is a project mainly written in Ruby, it's free.
Simple REST API for Lucene using jruby-jars
Rucene demonstrates how to build a simple REST API for Lucene using Ruby and
JRuby with jruby-jars.
To get started, just bundle install and then run ruby speakers.rb. Then go
to http://localhost:9092 to see the demo app. You'll notice in the logs that
it's communicating with a sinatra app running on 9091 -- that's the JRuby
application serving a Lucene index.