An implementation of Lisp whose syntax resembles a blend Emacs Lisp's and Scheme's, implemented in C using a Flex/Bison grammar with a bestline based REPL with just enough built-in OS interaction functions to do a little useful work, a pretty decent set of unit tests by way acutest and a set of in-language unit tests as part of its standard library (try (require 'tests).
Most of the completed feeatures work pretty well and pass their tests, but garbage collection hasn't been implemented yet (soon, I hope), so your programs won't live forever.
Some MacOS-specific features are used to resolve certain paths, so some (fairly small) adjustments would be necessary to get it running on other OSes.