So what? I was a Java dev myself. What does this mean?
There are even more millions of Javascript users. What does this mean, really?
>ABCL, FRANZ, ALLEGRO, SBCL, CLISP, GNU CL, Clozure might all be common lisp, but they are different implementations with different tools that will confuse a new person and several cost money.
Fear, Uncertainty and Doubt.
They all implement ANSI Common Lisp.
Right now i'm doing a project (not personal, it is for a company) and it runs on SBCL and CCL without any change. It would probably also run on ABCL straight away. It uses software transactional memory, bridges to C libraries and other stuff that isn't on the ANSI standard, yet it can also be written, very easily, in a portable way.
So, what you write is FUD.
>and several cost money.
More FUD. From your list, only Allegro CL (= Franz) costs money.
>Practical Common Lisp isn't very good in my opinion, that was the example i actually used. SICP is great for a mind-opening experience, but not super useful on how to write modern software and is why the creators dropped it at MIT.
SICP is not for writing modern software, is for understanding fundamentals. If you develop without having a solid grasp of the fundamentals, you become a "CODE MONKEY" (caps intentional), and this is what MIT is in danger of producing now (i'm not the only one to criticize the MIT for dropping SICP...)