It means what it says ;) All objects used by the Lisp are instances of classes from the class library, ie that stuff in class/ folder. These instances are ref

It means what it says ;) All objects used by the Lisp are instances of classes from the class library, ie that stuff in class/ folder. These instances are ref counted objects, as they are derefed and they drop to 0 refs they get deinited and freed. The Lisp is constructed from these, for example Lists in the Lisp are an instance of the class/vector, numbers are an instance of class/num, the environment is a chain of class/hmap etc. So yes, you do have GC if you don't make cycles, and you do have to care about not doing that just as you would in C++.