We can still call it "Hero's Quest" right? Sierra might've lost a trademark battle but IIRC the original was published and released as such and most of us only know the sequels by the new name.
Yeah, it's a bit confusing, but you're right. The first game was released under the name "Hero's Quest", but due to a licensing issue with Milton Bradley, the name had to be changed. So all the later games in the series are called Quest for Glory, as is the VGA remake of the original that was released in 1992.