since when YACC is in public domain ??

[Ozan Yigit]

I recently discovered that a version of YACC 
appereantly running under IBM PCs is being sold. For distribution price,
you get sources for what appears to be an early version of YACC. This
one showed up in a PDP-11 DECUS tape some time ago, and now being 
distributed, by someone named Scott Guthrey. 
The distribution also includes sources for a pre-processor
to yacc to handle attribute grammars, called PREP.

Does anyone know anything about this ?? Is yacc really on the public domain,
or is this an uninformed slip ? 

Oz	(wizard of something or another, no doubt..)
York University
Dept. of Computer Science
{decvax | ihnp4 | linus}!{utzoo | utcs}!yetti!oz