AutoSketch is actually a discontinued application. This means you won't have the possibility to obtain new versions of the software as well as licenses to use it since it was a commercial product. The old link that lead to the AutoDesk website is no longer working and there have been reports on the Autodesk forums that the product is nowhere to be found.
You will have to choose other applications from this category since AutoSketch is no longer available. At this point, your alternatives are: AutoCAD LT and Sketchbook Pro.