Basically they copied the filament part of a Cinemorph filter ( Anamorphic, Anamorfake, Anamorfaux — Vid-Atlantic Media Productions ) which you could get in a variety of colors for the little filament that goes across. At least their example appeared as a straight line across rather than convex, but I imagine that has more to do with the small sensor size and lens distortion that's usually corrected in the lens profile.
Would have been better utilized to have the custom aperture shape, but would require a different lens setup to be effective.