Are any parts of UNIX in public domain?

[Doug Gwyn]

In article <17555 at rochester.ARPA> ken at rochester.UUCP (Ipse dixit) writes:
>>It is interesting to notice that the previously very small (and fast)
>>shell procedure /bin/true now has a size of 747 bytes and a doubled
>>execution time.
>
>Oh, good grief! Do those lawyer types worry about somebody stealing
>a one-liner like exit 0?

More like a 0-liner.  Executing an empty shell script returns 0 status.
It's REALLY funny to put a copyright notice on an empty file; does that
mean that all those empty files you have lying around are illegal copies
of AT&T's /bin/true with the copyright notice removed?