The FAQ states:
Q: Is HTTrack Mac compatible?A: No, because of a lack of time. But sources are
available 

It is, and has been at least since version 3.32-2 (May 2004)

Simply download the "WebHTTrack/HTTrack : Linux/Unix/BSD..
Sources" version, decompress, cd to the folder and:

./configure
make
cd src
./httrack

How is that "not Mac compatible" ? It runs just fine - perhaps the question 
should be "Are there Mac binaries available" or something like that.