Download of ProEXR 2.5 for Mac was available from the developer's website 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. This Mac application is an intellectual property of fnord. The software belongs to Design & Photo Tools.
From the developer:
ProEXR is a set of 6 plug-ins to provide complete support for the OpenEXR file format in Adobe Photoshop and After Effects. Both Adobe applications include basic support for OpenEXR, but ProEXR provides access to important features of the format including multiple image layers, preservation of color space information, and choice between all compression options available in the latest OpenEXR libraries.
You may want to check out more software for Mac, such as Cuadro or Resize Now, which might be similar to ProEXR.