yacc: public domain?

[Doug Gwyn (VLD/VMB)]

You have hit upon the biggest problem with UNIX sites re-implementing
pieces of UNIX "in the public domain".  Namely, the person doing so
is constrained not to disclose any of AT&T's trade secrets.  If your
code ends up operating just the same as AT'T's and if you had access
to UNIX sources, it would be pretty hard to prove that you did not
use your privileged access to determine critical approaches embodied
in your own code.

If you really plan to do something like recode the YACC parser from
scratch, be sure you work entirely from unlicensed sources of
information (e.g. the UNIX manuals and journal articles).