Download of PixelStudio 4.66 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available.
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. PixelStudio for Mac lies within Design & Photo Tools, more precisely Viewers & Editors. This free software for Mac OS X is a product of Hippo Games.
From the developer:
Pixel Studio is a pixel art editor for artists and game developers. It is simple, fast and portable. No matter whether you are a beginner or a professional, you can create amazing pixel art anywhere and anytime. The tool supports layers and animations and has many useful tools to create cool projects. You can use Google Drive to sync your work between different devices and even platforms.
You may want to check out more software for Mac, such as Smith Chart for Mac, Movie2Shot or TVPaint Animation, which might be related to PixelStudio.