The licensed and supported libraries can be accessed via Nuget:
Duende IdentityServer does not contain any UI, because this is always custom to the project. We still provide you with the IdentityServer Quickstart UI as a starting point for your modifications.
Contains templates for the dotnet CLI.
You can install the templates using the following command:
dotnet new -i Duende.IdentityServer.Templates
You can find the Duende IdentityServer source code on GitHub.