No question that it is past the expiration date for freezer storage. What does that really mean?
If it has remained frozen without any power outages, or thawed, refrozen kind of stuff.... then it stands to reason that the pie has never been exposed to a temperature which would breed (or encourage the growth of) bacteria. From that standpoint, yes, you can eat it.
Here's the caveat: it might not taste the same as a "fresh one". Why? If you called Hershey they would tell you that they won't guarantee it. Basically the ingredients were not intended to be frozen for that long. Or, they never tested the stability of the ingredients to be frozen for such a long period. Either way, it's a gamble. Not a gamble in a "will I or won't I get sick?" kind of way. More of a gamble in a "is it going to taste good or not?" And there's really only one way to find out. (Let us know.)