Command key as a modifier

[Andrew Newell Mickish <am2q+@andrew.cmu.edu>]

How can I let my application percieve keystrokes that include the command key
as a modifier?  I am getting most keystrokes now, and I can check whether
the shift or control keys were down, but the keystrokes modified with the
command key don't get through at all.  I can live with MCL getting first
pick of keystrokes like CMD-X for cut, but what about the others?

Maybe more importantly, what are the conventions for using modifier keys
on the Mac?  Which is the "meta" key?  It seems to me that the OPTION key
should not be treated as a modifier at all, since it generates different
characters.  That is, it seems that OPTION-D should be treated as a "delta",
not as a modified "d".  Opinions?

--Andrew Mickish