Downloading CosmoDesktop 1.16 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free software for Mac is Pulsely Consulting. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. The application is included in Internet & Network Tools.
From the developer:
Cosmo Desktop lets you download pictures from the NASA Astronomy Pictures of the Day and set the desired image to be the wallpaper on your Mac. All astronomy pictures are courtesy of the NASA Astronomy Pictures of the Day under public domain, or their respective owners.
You may want to check out more software for Mac, such as Cosmo Desktop, which might be similar to CosmoDesktop.