In the show, Rumple claimed he created the Dark Curse, as mentioned in the S1 finale and in S2. By S4, its implied that someone else created the Dark Curse, and S6, establishes it to be the Black Fairy. The show has ALOT of inconsistencies and continuity issues, so we could just chalk it up to that. however we can say that both of these statements are correct:
The Black Fairy's version of the Dark Curse was created to banish all children to the LWM. The curse Regina cast, created Storybrooke, affected everyone, and erased their memories. My guess is that Rumple found the Dark Curse, and altered it, to be the curse that Regina cast. That way, both of these statements would be true. The Dark Curse originated from the Black Fairy, and Rumple "edited" to work the way it does.
I dont think this theory is a massive stretch, but in the more recent seasons, Rumple was never mentioned to have been the creator.