In MacOS, it's typical that normal application
functions use the Meta key. For instance, in all
applications, opening a new file is Meta-O, and
quitting is Meta-Q.
The meta key is known by different names in different
platforms. Apple calls it the "Command" key, Microsoft
calls it the "Windows" key, and Sun calls it the "Meta"
key. In any case, j does not support mapping events to it.
I've gone ahead and made a patch against 0.16.4 to
implement support for the meta key. It's only been
tested under MacOS X 10.2.1.