Free download:
Just unzip the archive to any folder on your hard disk and run the .exe. You can view the demo files by opening the file DG/Demo/1.dgf in DG with the help of "File/Open" command.
Additional files:
If the file Geometry.exe doesn't run on your machine, you should download and install the Microsoft® VB6 Runtime from the Microsoft website: vbrun60sp5.exe (1 Mb).