The MENU6.EXE program here writes a batch file CHOICE.BAT which contains the user's menu selection. MENU.BAT then runs CHOICE.BAT to start the program the user selected.
Unfortunately, DOSBox ignores CHOICE.BAT and runs it's own CHOICE command, resulting in the ".bat [Y/N]?" prompt, followed by program exit.
To fix this, we just need to copy CHOICE.BAT to another filename and then run that file, thereby avoiding the name clash with CHOICE. Here's a new MENU.BAT containing the fix:
copy choice.bat run.bat