do you have a dual layer burner? if so just use Disk Utility using this method.
- insert the Leopard DVD and open Disk Utility.
- click New Image in the toolbar and in the window that appears select where you want to save it and leave the Image Format at Compressed and Encryption at None then click save.
- after the image is created click Burn in the toolbar and select then select the image.
- burn it.
easy! i assume your using this for a personal backup?

. if you have a Mac Pro with dual superdrives i think you can bypass creating an Image but im not sure how to do that.
MacTheRipper is used to backup personal DVDs that are encrypted. if you burnt your own DVD or have a DVD with no encryption you can burn it using the same method above.