> They also tend to exclude Clojure.

As a CL (sbcl, mainly) I'm not interested in discussion about whether a language is a "true" lisp or not. I don't think that is a useful measure.

Something I recommend keeping in mind in classifying lisp-like languages would be based on how much code they share. With CL and Clojure, it is pretty much zero. This can lead to a practical understanding of differences and strengths.

I have a friend who is a long-time lisp guy who recently has made a living programming Clojure.