Another 'bare metal lisp' is http://www.ulisp.com/ , which has some fun demos and is supported by different hardware, 16 or 32 bit. It's also a single .ino file, e.g. [1]
[1] https://github.com/technoblogy/ulisp-arm/blob/master/ulisp-a...
[1] https://github.com/technoblogy/ulisp-arm/blob/master/ulisp-a...