It's been out a long time. I was playing with it in 2012 and I think it'd already been out a long time at that point. I think there is a blog post somewhere about a university student programming candy crush (or some other game) the night before it was due in NewLisp. Racket might also be worth a look again at some point. It's certainly heavier, but has a much larger community.

Picolisp is also really awesome and weird like NewLisp, but is really only for Unix. It is also small, but has plenty of features, and has been in development and supported since the late 80's. It is all written in C or Assembly (can't remember which one it is currently written in) and has built-in support for logic programming and all sorts of other things. It uses web browser for GUI, and can interop with Java and C.

Michael Fogus (blogger, Closure book author, and all around language nerd) wrote a fascinating article called "fleunpunkt lisps" (forgive spelling) that covers four really bizzare lisps (NewLisp, Pico Lisp, Wasp Lisp, and Arc). The summary is that they're neat and tried to do something revolutionary, but ended up just being odd.

Indeed great and very simple interop with C libs. I have looked and played with CL, Scheme, pico lisp, Clojure and Janet but keep coming back to Newlisp, because 'it just works' (for me), documentation is very good and has a lot of inbuild functions. Regarding the C interop I made some bindings for duckdb, termbox and libui at https://github.com/luxint.

Years ago we developed a web framework for newLISP called Dragonfly and used it for several projects. http://dragonfly.apptruck.de/