[TUHS] Copyright notices in Edition 5, removed in Edition 6

[ljb@merit.edu (Larry J. Blunk)]

   Apologies if this has been answered before, but I noticed
that there are AT&T copyright notices in the kernel sources
for Unix Edition 5, but they were removed in Edition 6.  You can
still see the comment blocks for the notices in Edition 6, but
the notices themselves have been removed.  Does anyone have the
history on this?

  I noticed that USL registered Editions 5, 6, 7 and 32V in
1992.  I would assume that Editions 4 and earlier are free
and clear because, prior to 1978, registration was a requirement
for protection.   Further, since USL waited longer than 5 years
to register the copyrights for 5, 6, 7 and 32V, these may be
free and clear as well.

  As I understand it, Editions 7 and 32V could have had copyright
protection without registration since they were released after
1978.  However, because they lacked copyright notices when
released, they may very well be considered public domain.  It was
not until 1989 that the requirement for including
copyright notices was dropped.