I have just released a new version of JRubyArt as a rubygem, it is confirmed as working on Debian and ArchLinux with OpenJDK 11 and OpenJDK17, it is intended to work with JRuby-9.3.1.0 (but also works with JRuby-9.3.0.0 which may be more readily available). But would grateful if a Windows or MacOS user could give it a go. There is brew formulae for JRuby-9.3.0.0. For Windows I think it comes with an installer.
If you are MRI ruby user, it possible to get away without installing jruby to your system by doing a post install download of JRubyComplete using the gem command.
k9 --install
Which also installs the JRubyArt examples to k9_samples folder. If you open a console and change directory to the k9_samples folder you can autorun a selection of the examples using the rake command.