It is a foul when an ineligible offensive player, which is difficult to describe but is often an offensive lineman, advances beyond his line of scrimmage after losing contact with an opponent at the line of scrimmage. It is also illegal when an ineligible offensive player moves downfield without contacting an opponent at the line of scrimmage. These restrictions end when the ball leaves the passer's hand. The offending player must be more than one yard beyond the line of scrimmage prior to the pass to be illegally downfield. This guideline is used in college and professional football.
From the 2006 rules:
Article 2 It is a foul when an ineligible offensive player (including a T-formation quarterback),
prior to a legal forward pass:
(a) advances beyond his line, after losing contact with an opponent at the line of
scrimmage;
(b) loses contact with an opponent downfield after the initial charge and then continues
to advance or move laterally; or
(c) moves downfield without contacting an opponent at the line of scrimmage.
The above restrictions end when the ball leaves the passer’s hand.
Note: The guideline for officials to use for an ineligible player(s) to be illegally downfield: the
offending player must be more than one yard beyond the line of scrimmage prior to the
pass.
See rulebook:
http://blogmedia.thenewstribune.com/media/2006 NFL RULEBOOK.pdf
Guorde was 1 yard down the field.. Kosier was still in contact with his player, even though he was "down the field"
Since Kosier was still in contact(he pancaked the guy), and Guorde was 1 yard down the field.. I don't see how this is a penalty.