Is the Whirling Dervish AT for Swashbuckler limited to followers of the Dawnflower only? Don't see anything in the description, but alot of the flavor points that way
its definitely flavored after sarenrae but i dont see anything specifically restricting it to worshipers so id say its open for everyone.
I'd clear it with your GM. While there isn't a strict requirement I would require worship of Sarenrae at the very least - or maybe a paragraph or two re-flavouring it for any game I GM.