When I close the LKB Top Menu, is Lisp supposed to exit as well?
That depends on whether you're running from source or a precompiled
version of the LKB, and on how you close the LKB Top Menu. In general,
clicking the X in the upper right or left hand corner is not the
recommended fashion of closing the LKB Top Menu. Rather, choose Quit > Confirm Quit
from the menu itself. In this case, if you are running from precompiled
code, the Lisp image will halt as well. If you are running from source,
your Lisp will still be alive.