iconGen 1.1 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.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The software relates to Design & Photo Tools. The actual developer of this free Mac application is Alexander Stein.
From the developer:
Generating icons and assets by hand for your applications is a huge hassle that involves several rounds of resizing and renaming image files in order to fit the various resolutions needed.
iconGen expedites this process and allows you to take a source image and immediately generate a folder for your macOS, iOS, and watchOS icons and assets to be added to your project folders after dragging your image in and selecting the target platform.
You may want to check out more Mac applications, such as Smith Chart for Mac, Movie2Shot or Piranesi, which might be related to iconGen.