I hate to disagree with Bert since it almost always means I'm wrong, but Microsoft did not intend for Line of Business applications to be installed on the SBS 2008 Server. It's just doing too many other things with too much automation to include another instance of SQL. For folks with SQL LOB apps they want peeps to get the SBS 2008 Premium which includes a separate SQL 2005 or 2008 license. That said, there's probably not much reason that a SQL Lite instance wouldn't run on the SBS 2008 Server, but if you tried to install full SQL 2005 the system should try to stop you. I think the automation for SBS 2008 relies on SQL so there is already some sort of database installation.
