It's basically a ruby port of tiddlylisp, as seen on http://www.michaelnielsen.org/ddi/lisp-as-the-maxwells-equations-of-software/ via HackerNews.

Learn ruby and lisp.

• This is not a serious project, it was made for learning purposes.
• This project is unrelated to http://github.com/erik/lispr , aside from sharing the goal of interpreting lisp on ruby.

Ruby 2.0 or greater

run ruby littlelisp.rb and interact with the REPL.

You know, the usual, fork and create Pull Request.

GNU GPL v3

...

I think it means that I do not provide any warranty, and you can copy and distribute it freely.