CAL, IIS, SQL Server

Question

Hi.

I have been searching the web about information regarding how licensing works when an IIS service access SQL server.

This is the scenario:

1 IIS Server running webservice.
1 SQL Server.

Multiple clients/users (Webservice calls) logging in to the website using ASP.NET forms or other autentication in open source db
ie the users are NOT logging on to the SQL Server using windows authentication or SQL authentication.
It is only the webservice that is logging on to the SQL server.

Do i need Single user CAL for each user on my website?

Since we cant get information about this we ar considering migrating to another database platform, thus we realy love SQL Server.