free alternative to DVDFab for OS X?
Handbrake is a great free utility for ripping DVDs. It does require the free libdvdcss but the first time you try and rip an encrypted DVD Handbrake will prompt you to download and install it. It's pretty easy.

That will get you a movie file of your choice but not an .iso. There are apps that will do that. iMovie, iDVD, Toast, etc. will all take a movie file and burn it to a DVD or .iso