This package appears to have a custom/proprietary license agreement, and ProGet cannot be automatically determine the license type. You'll need to assign a license type to the URL to allow or block packages with this license.
To install InedoIcons from the command line, run the following command:
nuget install InedoIcons -Version 122.0 -Source https://proget.inedo.com/nuget/NuGetLibraries/v3/index.json
To install InedoIcons from the Package Manager Console within Visual Studio, run the following command:
Install-Package InedoIcons -Version 122.0 -Source https://proget.inedo.com/nuget/NuGetLibraries/v3/index.json
For projects that support PackageReference, copy this XML node into the project file to reference the package.
<PackageReference Include="InedoIcons" Version="122.0" />
Contains lots and lots of icons.