SmartDupe 1.0 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. The software lies within System Tools, more precisely File Managers. 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.
From the developer:
SmartDupe is bash script which replaces file Duplicates in a given path by Hard links to free space on your Hard Drive.
Works for UNIX Based Systems Mac OS X and Linux
You may want to check out more software for Mac, such as Open.nuke folder, Butterflyzer or FileVaporizer, which might be related to SmartDupe.