It might take longer and be more manual, but you should be able to get the rar files individually using your browser.
FRD and JDownloader are useful tools to make it easier, but not essential.

If you keep going a bit to section 3, step 7, instead of copying all the links into FRD, you can visit each link individually, and download the partial files like that.

After you’ve gotten all the files manually, you’ll basically be able to resume at ~step 10 or so.

The other option is to figure out why java/mac/FRD aren’t getting along in your case. But that might be more trouble than it’s worth.