Download it all with
wget -r -A.pdf http://www.gameaipro.com/
wget -r -A.zip http://www.gameaipro.com/
wget -r -A.pdf http://www.gameaipro.com/
wget -r -A.zip http://www.gameaipro.com/
a) sell PDF ebooks
and
b) explicitly say that you are not supposed to re-upload the content elsewhere.
And load does not translate to cost for everybody. If you saturate the connection to my VPS, I don't pay more, it just gets slower for everybody in contention. I can spin up mirrors but if I'm offering a free resource like this, I'd be more likely to limit the bandwidth-per-client-IP or just actively let it run slow. They could even limit the bandwith to the subdirectory with...
location /download/ {
limit_conn addr 1;
limit_rate 50k;
}--wait=5000 --random-wait
Done...