I will be building an n-tier app based on Windows NT and SQL server using a browser and plain HTML as the front-end.

Is there a special licensing for both of these products if users won't be authenticating? Also, would any of the users need to authenicate or have the NT or SQL client loaded other than me the developer? And thirdly, how are users authenticated (ie put in their user name and password) in an n-tier application? Is this passed off to SQL Server or NT or does the application take care of this?