CosmAtlas 1.0.5 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This Mac application is a product of Aurelio Calegari. The program lies within Education Tools, more precisely Teaching Tools. We recommend checking the downloaded files with any free antivirus.
From the developer:
CosmAtlas is a powerful Milky Way simulator for iPhone, iPad, and Mac, which applies real physics to calculate every single celestial body position at any time between the year 0 to year 9999.
With this educational app, you'll be able to navigate across the astronomical distances in outer space, land on the major planets and satellites, and see the sky from there or read about it.
You may want to check out more software for Mac, such as ChordPhobia, Learn To Draw or Fast Rabbit Typing, which might be similar to CosmAtlas.