Although I personally dont have a Dual Layer Burner yet (the burners themselves are now dirt cheap, its the flipping media that is a bit too pricey for my liking), but I'm sure the easiest way to copy disc to disc would be just to rip the files to an ISO image using DVD Decrypter then burn the ISO back to your Dual Layer disc using the same software?
I hope the files you are downloading from Limeware are public domain. Otherwise, burning the stuff you download is considered illegal.