You can do it all with free software. That is free as in both freedom and gratis.
I run Debian and this is how I do it:
Use lsdvd to check the disc contents and identify which track number and audio track I want.
Use mplayer with -dumpstream and -dumpfile options to dump that track to a vob file on hard disk.
These kind of dumped vobs can have timestamp errors so I use mkvmerge to mux the vob into matroska container; doing so automatically corrects that issue and also gives me the option to discard any video, subtitle or extra unwanted audio track.
I now have a matroska file containing only the audio track I wanted. Sometimes this means I'm done.
The audio could be anything from mp2, Dolby 2.0, Dolby or DTS 5.1. Depending on what I want to use the audio for I might now downmix it to two channels and/or transcode the audio to mp3 or vorbis or m4a or similar. If it's two channel Dolby or mp2 I'll just leave it as is. If it's 5.1 and I intend to play it back on a two channel device I will downmix it using my own bash script which uses mplayer's -pan option to do a decent job of properly downmixing the low frequency, surround and front channels into a nice sounding two channel stereo track and also transcoding and normalising if I choose.
The same tools are available for Windows and Mac. There is also ffmpeg which can do everything except dump the files from DVD to hard disk.
There are several graphical apps which let you do all the same things without using a terminal or command line but I found most of the graphical apps I tried tend to be either hideously complex or so simplistic as to be useless. There are also lots of poor apps which try to scam you into buying software which is only a low quality interface to tools available from their original authors at no charge. I suspect that VLC might be the easiest way to go if you prefer a graphical tool or only do this task occasionally. There is a reasonable guide for DVD audio to mp3 at http://www.wikihow.com/Rip-DVD-Audio-to-MP3-Using-VLC-Media-Player
Remember the process is essentially simple:
Dump to hard disk the audio track (or dump audio+video then discard the stuff you don't want)
That might be all you need, but maybe you also want to:
downmix to 2 channels
transcode to mp3 or m4a or similar.
That all there is to it, so don't get persuaded you need some expensive or complex apps to do this. If you find yourself using a very difficult or complex interface or about to hand over money then stop and look elsewhere.Edited by julian67 - 7/28/13 at 2:20pm