>>>Hi everybody, I want to begin developing a commercial application using VFP 9 as my front end and a free RDBMS (not DBFs) as the back end. I'd like to know what is the best one to work with VFP9. I have in mind 3: PostgreSQL, Firebird, and MySQL. I've never worked with them and of those three I guess MySQL is not completely free. I would like to know from the ones that have had any chance to work with any of those databases or perhaps any other that you may consider as a better alternative.
>>>
>>>TIA
>>
>>SQLExpress IMHO. This gives you most of the features of SQL Server (including reporting service) and direct scalability to huge databases. Free.
>
>Thanks for the advice, but, I guess you have to pay for using Reporting service, right? I'm not sure about it.

No. It is free. See http://www.microsoft.com/sqlserver/en/us/editions/express.aspx

Update - see here also.. http://msdn.microsoft.com/en-us/library/ms365166.aspx