FreeFileSync Forum

Done

You can either put that in a file.rb
And run this:
brew install --debug --verbose --cask [nameoffile].rb

or you can use my repo:
brew tap marcuzzz/homebrew-marcstap
and just run brew install freefilesync

https://github.com/Marcuzzz/homebrew-marcstap/blob/master/Casks/freefilesync.rb

I just created / tested this cask, seems to work...

cask 'freefilesync' do
version '12.1'
sha256 :no_check

url "https://freefilesync.org/download/FreeFileSync_#{version}_macOS.zip"
name 'freefilesync'
homepage 'https://freefilesync.org/download.php'

auto_updates true

pkg "FreeFileSync ...