Downloading Stochas 1.3.9 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. We recommend checking the downloaded files with any free antivirus. The application relates to Audio & Video Tools. The actual developer of this free Mac application is Surge Synthesizer Team.
From the developer:
Stochas is an open-source advanced probabilistic polyrhythmic sequencer plugin. Stochas is at its core a step sequencer, which means it generates MIDI notes. As such, it does not generate any sound of its own but can be used to sequence other plugins and/or hardware synthesizers. Although it can be used for basic step sequencing, its main function is to provide randomness to the step sequencing process.
You may want to check out more Mac applications, such as Mixtikl 5, Noatikl 2 - Generative Music Lab or HighC, which might be similar to Stochas.