Chicken Scheme is a specific Scheme implementation, Common Lisp is a language with three dozen implementations. Free CL from day zero: CMUCL. CMUCL originates

Chicken Scheme is a specific Scheme implementation, Common Lisp is a language with three dozen implementations. Free CL from day zero: CMUCL. CMUCL originates in Spice Lisp (1980), from before Common Lisp. CMUCL has spawned commercial and free variants (SBCL). Free: CLISP, 1987. Free: GCL, 1994. Still, Chicken Scheme is great! Though I prefer CL.