Yer new here, so you probably don't know..
This was debated back and forth for years, until at last someone got ahold of the Mattel Style guide that they sent to people who wanted to licence MOTU for their products. In that guide, it clearly states that he is just a henchman, not a ghost, not a future Skeletor.
When the package describes him as the Ghost of Skeletor, it is meant as "A ghost who works for Skeletor," not "the disembodied spirit of Skeletor."
That was from Mattel, and hence, official and canon.