> I seem to remember that it's executable on Mac PowerPC only.

Now see what you made me do. 8-)

     http://www.stuffit.com/win/seabuilder/index.html

It looks like Aladdinsys re-purposed the extension. That probably 
earned them a few more raspberries.

Anyway, my memory is that .sea archives were around before stuffit, 
which would be before the PPC platform. Perhaps the current 
distributions are being compressed by a version of stuffit that no 
longer supports PPC/68K fat? If that's the case, can they be opened 
with a fat version of stuffit or expander?

(I own stuffit 4.5 and I've never had problems with netbsd 1.5.x; 
haven't tried 1.6.x yet, although I probably will pretty soon, now that 
I have broadband access.)

reiisi