MKS Toolkit/UNIX [r] System, SEA ARC/PKARC, ...

[Charles Hedrick]

Look and feel isn't as general as you're implying.  In general, all
people copyright is their actual code.  If you're tricky, you may be
able to patent the actual function that is being done, so that
somebody could reimplement it and still be covered.  (This is normally
done only for applications that involve special-purpose hardware, but
there is sometimes a way of describing what looks to most of us like
software as a piece of hardware that happens to contain a memory that
is running this program.  You'd have to talk to a lawyer to figure out
how far this can really be pushed.)  But patents are a pain to deal
with and this isn't often done.  The look and feel stuff is normally
done by copyrighting the thing as an audio-visual work.  This means in
effect that it is being treated as a work of art and you're
copyrighting the displays.  I think this is highly questionable even
for the cases where it is being tried, but I've never heard of anyone
trying it with a standard Unix utility, which isn't display-oriented.
And even if you succeeded, somebody could produce something that did
the same thing and had a different display format.  As far as I know,
nobody has yet produced a legal theory under which the behavior, as
contrasted with the code, of a Unix utility can be protected.