The company calls the position "Captain" in their job postings, so it's "Captain" according to them. Besides, they do sometimes have "First Officers" on some flights - I believe only when some things are MEL'd like the the autopilot or something like that.

Maybe their op specs require two pilots in some situations. I believe that Alpha Flying out of NH (they fly the PC-12) are operating traditionally single-pilot planes with a two person crew because of the op specs, so in that case the PIC is "Captain" too, even though flying a plane that was built for single-pilot ops.