Charles Oliver Nutter, Thomas Enebo, and Ola Bini have posted the third release candidate of JRuby 1.0, a "1.8.5 compatible Ruby interpreter written in 100% pure Java." It also supports the Bean Scripting Framework.
This will likely be our final release candidate before our 1.0 release. People are encouraged to try out this release to help us find any remaining showstopper issues. We have spent a lot of time over the last month squashing compatibility bugs and we have confidence that applications 'will just work' (tm)*. Please try your applications and libraries against JRuby and give us feedback.
JRuby is distributed under three licenses CPL, GPL, LGPL. That's just way too confusing. There's zero-need to dual license under both the LGPL and GPL since the LGPL explicitly allows code to be forked into a pure GPL product.