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
JRuby offers the advantage of running on the Java Virtual Machine, enabling integration with Java and better multi-threading. In contrast, Ruby excels in simplicity and rapid development, particularly in web applications, but may struggle with performance in concurrent scenarios.