S4A 1.6 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. The application lies within Developer Tools, more precisely IDE. This free Mac app is an intellectual property of edu.mit. We recommend checking the downloaded files with any free antivirus.
From the developer:
S4A is a Scratch modification that supports simple programming of the Arduino open source hardware platform. It provides new blocks for managing sensors and actuators connected to Arduino. There is also a sensor report board similar to the PicoBoard.
It has been created to attract people to the programming world.
You may want to check out more software for Mac, such as Objective-Basic or RapidSVN, which might be related to S4A.
IDE