When attempting to starting the LispWorks X11/Motif GUI when the required version of Motif is not installed, LispWorks prints the error message:
Error: Could not register handle for external module X-UTILITIES::CAPIX11:
dyld: /Applications/LispWorks 5.1/lispworks-5-1-0 -macos-universal-motif can't open library: /usr/local/lib/libXm.4.dylib (No such file or directory, errno = 2)
Ensure you install Motif as described in The X11/Motif GUI. Restart X11.app and LispWorks after installation of Motif.