IdentityServer4 - licensing information updates (dotnet#23698)

* Remove the OSS-mention from general description

The IdentityServer is not an open-source, sot it's general description
has been updated with no OSS mentioning.

* Describe licensing options for IdentityServer

Author: BartoszKlonowski

docs/architecture/cloud-native/identity-server.md

@@ -6,7 +6,7 @@ ms.date: 05/13/2020
 
 # IdentityServer for cloud-native applications
 
-IdentityServer is an open-source authentication server that implements OpenID Connect (OIDC) and OAuth 2.0 standards for ASP.NET Core. It's designed to provide a common way to authenticate requests to all of your applications, whether they're web, native, mobile, or API endpoints. IdentityServer can be used to implement Single Sign-On (SSO) for multiple applications and application types. It can be used to authenticate actual users via sign-in forms and similar user interfaces as well as service-based authentication that typically involves token issuance, verification, and renewal without any user interface. IdentityServer is designed to be a customizable solution. Each instance is typically customized to suit an individual organization and/or set of applications' needs.
+IdentityServer is an authentication server that implements OpenID Connect (OIDC) and OAuth 2.0 standards for ASP.NET Core. It's designed to provide a common way to authenticate requests to all of your applications, whether they're web, native, mobile, or API endpoints. IdentityServer can be used to implement Single Sign-On (SSO) for multiple applications and application types. It can be used to authenticate actual users via sign-in forms and similar user interfaces as well as service-based authentication that typically involves token issuance, verification, and renewal without any user interface. IdentityServer is designed to be a customizable solution. Each instance is typically customized to suit an individual organization and/or set of applications' needs.
 
 ## Common web app scenarios
 
@@ -37,7 +37,14 @@ IdentityServer provides middleware that runs within an ASP.NET Core application
 
 ## Getting started
 
-IdentityServer4 is open-source and free to use. You can add it to your applications using its NuGet packages. The main package is [IdentityServer4](https://www.nuget.org/packages/IdentityServer4/) that has been downloaded over four million times. The base package doesn't include any user interface code and only supports in memory configuration. To use it with a database, you'll also want a data provider like [IdentityServer4.EntityFramework](https://www.nuget.org/packages/IdentityServer4.EntityFramework) that uses Entity Framework Core to store configuration and operational data for IdentityServer. For user interface, you can copy files from the [Quickstart UI repository](https://github.com/IdentityServer/IdentityServer4.Quickstart.UI) into your ASP.NET Core MVC application to add support for sign in and sign out using IdentityServer middleware.
+IdentityServer4 is available under dual license:  
+
+* RPL - let's you use the IdentityServer4 free if used in open source work
+* Paid - let's you use the IdentityServer4 in a commercial scenario
+
+Please reach out to official [Product's pricing](https://duendesoftware.com/products/identityserver) page.
+
+You can add it to your applications using its NuGet packages. The main package is [IdentityServer4](https://www.nuget.org/packages/IdentityServer4/) that has been downloaded over four million times. The base package doesn't include any user interface code and only supports in memory configuration. To use it with a database, you'll also want a data provider like [IdentityServer4.EntityFramework](https://www.nuget.org/packages/IdentityServer4.EntityFramework) that uses Entity Framework Core to store configuration and operational data for IdentityServer. For user interface, you can copy files from the [Quickstart UI repository](https://github.com/IdentityServer/IdentityServer4.Quickstart.UI) into your ASP.NET Core MVC application to add support for sign in and sign out using IdentityServer middleware.
 
 ## Configuration