Comment by ofrzeta
related: "In Version 2.5, AutoLISP allowed access to the DWG database. AutoLISP was based on XLISP, a public domain version of LISP written by David Betz. Betz later complained that Autodesk had failed to acknowledge the source, which the company later did." (https://www.shapr3d.com/history-of-cad/autodesk-and-autocad)
Thanks for the link! I didn't know about the XLISP controversy.
My interpreter doesn't aim for full compatibility - just enough to run the schematic generation workflow from 1991. The core is: defun, setq, car/cdr, recursion, and the (command ...) interface to draw entities.
The interesting part was how templates could trigger other templates - inserting a contactor (Schütz) would automatically generate its coil in the control circuit. Code writing code, classic LISP.