You can download it but it involves quite a number of files and to be honest it's easier to buy a copy on ebay. I only paid £2.69 for my latest copy, which unlike earlier copies allows you to get automatic updates. My current version includes all four major VAG manufacturers, Audi, VW, Skoda and Seat. When you buy a copy on ebay you also get detailed instructions on how to install the software.
If you do buy a copy and get any problems sent me a PM and I will try and help if I can.