The latest version of VisualDSP++ tools, VisualDSP++ 5.1.1, can be downloaded from the VisualDSP++ Development Software Product Page here. Note the download file has a *.exe extension not a *.vdu extension as VisualDSP++ 5.1.1 is a separate installation to VisualDSP++ 5.0 rather than an Update.
When installing 5.1.1 you have the option to copy over the license from your existing version. To do this click on 'Advanced' when the installer asks for the installation path and check the box to enable copying over a license.
One of the main features of VisualDSP++ 5.1.1 is that it offers support for the ICE-1000 and ICE-2000 emulators. This, along with details of other important features can be found in the Release Note which is also available from the Product Page or by clicking here.