JRuby is an implementation of the Ruby programming language atop the Java Virtual Machine, written largely in Java. It is free software released under a three-way EPL/GPL/LGPL license.
License: Open Source
REBOL is a lightweight, flexible language ideal for rapid prototyping and network applications, but it suffers from limited community support and performance issues. In contrast, jRuby, being a JVM language, offers better performance, a rich ecosystem, and strong community backing, making it more suitable for web applications and large-scale projects.