Ha! The program you linked to , HTTrack, will run on a Mac, too, and it worked really well for me.
You'll need to compile it yourself, though (or use Macports or Homebrew which I don't know much about) and I know that compiling stuff is not everyone's cup of tea...
(About a year ago the latest version was "httrack-3.48.13.tar.gz" and I ran into compilation errors I couldn't resolve. However, slightly older version "httrack-3.47.27.tar.gz" compiled easily with no errors, and ran perfectly for my needs. The current version is "httrack-3.48.21.tar.gz" so you'd want to try that first, of course.)
I used SiteSucker to download a website and it took about 2GB of space. But when I checked again about 6GB of my space was gone! I deleted and it seemed to recover up to about 2-3GB, but then I checked later on and that much was lost again. I only have 5GB of storage left!