The 1.6.2 version of ChemDuet for Mac was available as a free download on our website. The application is included in Education Tools. The actual developer of this software for Mac is Synergy Creations.
From the developer:
ChemDuet is the premier chemistry reference tool for your iPod. ChemDuet gives you quick access to atomic properties, wherever you go with your iPod. The included data is based on Synergy Creations' award-winning Periodic Table software. Easily adjust units of properties stored on iPod.
You may want to check out more Mac applications, such as Genealogy Pro, sciatrope or Curvus Pro X, which might be related to ChemDuet.