Board Thread:General Discussion/@comment-4821842-20151114051347/@comment-25926288-20170411110754

Rumple created the curse as in he manufactured it from its original form to include a Savior.

The origin post season 3 has been consistent that Rumple merely found the base spell then changed it from there. So, retconned, but not that inconsistent. Seasons 1-3 it was simply believed to be Rumple. Seasons 4-6 said it wasn't Rumple.