Sin is a word that has been abused.
The Source tells me that it means “to take the way of Karma” – that being, to freely and willingly adopt a path that reduces ones frequency – taking you further away from your creator.
“Original Sin” is therefore the Karmic content (low frequency attractivity) that one has accrued in previous incarnations. Its reduction being the whole point of the current incarnation.
Living a “Sinless” life or “out of Sin” is a life being lived in avoidance of Karma – taking the path that leads to daily communion with God.