Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA
Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!linus!philabs!cmcl2!seismo!brl-tgr!tgr!lcc.jbrown@UCLA-LOCUS.ARPA
From: Jordan Brown <lcc.jbrown@UCLA-LOCUS.ARPA>
Newsgroups: net.unix-wizards
Subject: PD yacc
Message-ID: <8293@brl-tgr.ARPA>
Date: Tue, 12-Feb-85 21:07:49 EST
Article-I.D.: brl-tgr.8293
Posted: Tue Feb 12 21:07:49 1985
Date-Received: Sat, 16-Feb-85 06:21:51 EST
Sender: news@brl-tgr.ARPA
Organization: Ballistic Research Lab
Lines: 2

I believe the Software Tools folks have a yacc in Ratfor which is PD.
You might try contacting dpm@lbl-csam.