Download of mAC3dec 1.6.3 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. The actual developer of this free Mac application is Lukifer. The application lies within Audio & Video Tools, more precisely Editors & Converters.
From the developer:
mAC3dec is an application that decodes AC-3 audio from DVDs or QuickTime audio and spits back AIFF, MP3, or AAC files. You have the option to adjust the normalization value when necessary. In addition, the tool can save all files at once when choosing the destination.
You may want to check out more software for Mac, such as MFilter or Aiseesoft WMV Converter for Mac, which might be related to mAC3dec.