Bizarrely, SuperMicro doesn’t appear to have ever tested it, because double-clicking on the downloaded IPMIView20 application doesn’t do anything. This is because someone forgot to set the execute permission on the installer.
Supposing it’s in your downloads folder, open up Terminal and run the following commands:
cd /Users/$( whoami )/Downloads/IPMIView20.app/Contents/MacOS
chmod u+x IPMIView20
This will open up the installer for you. Once it’s installed, it will show up in your Launchpad like a normal application.