Charles Oliver Nutter, Thomas Enebo, and Ola Bini have released JRuby 1.1, a "1.8.6 compatible Ruby interpreter written in 100% pure Java." It also supports the Bean Scripting Framework. This release focuses on improving performance, and should outperform the native Ruby interpreter for many tasks. JVM: it's not just for Java any more.
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.