Download of APOD 3.09 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. APOD for Mac lies within Education Tools, more precisely Science. This free Mac app is an intellectual property of Adam Mazur.
From the developer:
APOD is a very simple NASA Astronomy Picture of The Day browser. The application allows you to watch and enlarge photos, watch videos, save any image to disk, share photos and videos with others, mark any photo and video as a favorite, and watch only those. APOD also provides a widget presenting today’s picture.
You may want to check out more Mac applications, such as Pic-a-POD, MozoDojo or Juu Background, which might be similar to APOD.