Right now setup-bggraphics.tp2 refers to tisunpack on Linux and OS X as bggraphics/tiz/tisunpack. But instead of Windows where bggraphics ships a bggraphics/tiz/tisunpack.exe no bggraphics/tiz/tisunpack is shipped. So please either also ship a bggraphics/tiz/tisunpack or simply refer to tisunpack without the path, which should pick up the tisunpack shipped with WeiDU on these systems.
Oh and a version with a fixed bggraphics.tph would be great too.