The 2.5 version of SuperPNG for Mac was available as a free download on our website. The program lies within Design & Photo Tools, more precisely Viewers & Editors. This free Mac application was originally created by fnord software.
From the developer:
SuperPNG is an open source Adobe Photoshop plug-in for using PNG ("ping") files. It has more comprehensive support for the format than Photoshop's included plug-in and provides control over alpha channel handling. It includes some additional options for saving PNGs: Alpha channel control, Variable Compression, Smart Quantization, ICC profile embedding and Meta Data saving.
You may want to check out more software for Mac, such as Cuadro or Resize Now, which might be related to SuperPNG.