The semantics of the function
lw:set-quit-when-no-windows
have changed slightly in LispWorks 6.1. It is now documented, in the
LispWorks User Guide and Reference Manual
In LispWorks 6.0
lw:set-quit-when-no-windows
was undocumented and its semantics depended on the original value of the
:quit-when-no-windows
delivery keyword.
LispWorks Release Notes and Installation Guide - 23 Dec 2011