1) If I have a mobile application database written in SQL Server which has SQL Server CE databases on PDAs synchronising with it, can I get away with no licensing cost if I use the SQL Server Express Edition?
2) SQL Server <> SQL Server (Mobile Application Database) <> SQL CE If we then complicate the model as the mobile application main SQL Server database has a service runninhg which then synchronises via .NET and web services to another database that is SQL Server based, does this cause problems with licensing, e.g. in the area of multiplexing because we know our ultimate end PDA users?
3) Oracle <> SQL Server (Mobile Application Database) <> SQL CE How would licensing be affected if the backend system is changed to Oracle.
Thanks.
SQL Express Edition is free to use - it's got it's limitations but if your app can work inside it's constraints then it's fine to use.
You're not clear on point 2 but if all of those SQL installations are Express or CE/Compact then that's fine as well.
You license costs would come in if you put a Standard/Enterprise edition SQL Server in the mix at which point you either need to look at CAL licensing or get Proc license(s).