AC3 Codec 0.4 for Mac was available to download 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 application belongs to Audio & Video Tools.
From the developer:
AC3 Codec is a QuickTime component which allows the playback of AC3 audio in AVI files. The component uses the liba52 library for the AC3 decompressing, you can get more information on this library at http://liba52.sourceforge.net/.
You may want to check out more Mac applications, such as AC3-DTS Killer, codecity or TryToAC3, which might be similar to AC3 Codec.