Downloading Filtre & Go 0.6 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The software is included in System Tools. 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.
From the developer:
Filtre & Go is the first generic filter for EIMS. It provides headers, server ID, return path and body filtering with case sensitive and insensitive regular expression and literal strings. It honors DNS exclusions, provides test modes and updates filters on the fly. Filtre & Go is a free and an open source (BSD-Lite license) project. Binaries are provided for 68K, PPC and Carbon.
You may want to check out more software for Mac, such as Unlink, which might be similar to Filtre & Go.