Edit source.lsp , change "Cancel" to "Exit" . Then use the Visual LISP Editor (VLIDE) inside AutoCAD to recompile it back to a new VLX.
Advanced users sometimes use debuggers to monitor AutoCAD’s memory while the VLX is running. Since the interpreter eventually has to read the instructions to execute them, bits of the logic can be "scraped" from the system RAM. This requires significant knowledge of assembly and LISP internals. Challenges and Ethical Considerations vlx decompiler
This time, it finished.