The fact that VCDS is a dealer level computer programming and the amount of things it can do with all post '92 VW, Audi, Seat or Skoda cars is the reason its so dear. I do agree its a bit pricey if you just want to read the odd fault code or clear service interval messages, but any intention of fitting non-spec parts to your car (like cruise control) and its worth every penny.
And sadly no distributions of Linux/BSD (Apple)/Unix are supported yet.