Rails and mssql

My company is developing an application for a customer. The customer
have an ASP.NET web site and SQL Server 2008 database.

The client wants to keep SQL Server 2008 database and he is
complaining that ActiveRecord does not communicate natively with SQL
Server 2008.

They are asking us why ActiveRecord uses freeTDS in conjunction with
unixODBC. Actually I googled it a little bit and in fact, I wasn’t
able to find any library using only freeTDS to connect to SQL Server
neither why there are only libs using freeTDS + unixOBC.

Does anyone have any idea?

Thanks in advance.