If you find that you need to copy an unprotected DVD on your Mac (I am using El Capitan), I found these helpful steps on Apple’s forum. User PPalm_1 states:
1. With the DVD you want to copy in the disk drive, open Disk Utility. (Remember, this works ONLY with non-copy protected disks.)
2. After all of your drives have been found with the utility, click on the TITLE of the DVD in your disk drive
3. at the top of the screen go to File…New Image…Image from…(whatever your DVD is called).
4. a window will open offering you some options: name the disk image whatever you want (or keep it the same as the inserted disk), choose the Desktop for the location of the new image, and select Format: “DVD/CD Master”
5. hit save and the utility will take a few minutes to READ the current DVD, and it will create a disk image file with the name you selected and place it on your desktop. If, when it is finished, you can’t find it, open Finder, click on Desktop, and find the most recently created .cdr file. That’s the one!
6. Now right click on that file and select “Burn Disk Image …to disk” and follow the instructions.
7. From here on out, you can keep doing #6 above, and make as many copies as you like.
To read PPalm_1’s full response you can see the post here!