The problem with DVD decoders is that either they can't handle the encryption of DVD disks or they fill up your hard drive with huge amounts of decrypted data.
This is not so however with Fairmount which decrypts DVDs on the fly directly from the DVD drive as other applications access it. The advantage of decoding a DVD means that you can access it instantly from other third party app. In this case, it seems that VLCPlayer is the recommended option and Fairmount can decode a DVD for direct reading by VLC Media Player. In fact, according to the developers it won't work with any app which is a bit annoying although if you're going to choose any media player to associate with, then VLC isn't a bad choice.
Alternatively, Fairmont can be used to backup your DVDs by dragging the VIDEO_TS file to a backup drive or simply onto your hard drive if you've got space. This seems a bit pointless however when the obvious big advantage of Fairmount is that, if you have a Dual Layer DVD Burner or DL DVD, you can backup any movie in one step although you'll need the developer's DVDRemaster (which comes bundled with this download) to burn it.
Fairmount is a simple, elegant and effective application for allowing backups of your DVDs or copying on the fly.