first: rip the DVD to your harddrive, you can use mactheripper
second: depending on what size DVD you can burn you will need to compress the file to fit on one DVD, you can use DVD2oneX
then burn those files using the finder
I have been using this methode for years so it might not be the fastest or the most efficient but it has always worked so I haven't looked into anything else. There will be others who will tell you about newer and better programs but this works.