Interbase is seen (from his corporate perspective) as a database tossed off to Open Source when the company was not interested in supporting it any longer.

Even if it is now freely available, and has an active developer set, it doesn't mean squat to us when we find a particular problem when our 3rd party software that conflicts with it. The cost of SQL Server is nothing compared to the cost of NOTHING happening on a project while we wait for the showstopper to be resolved.

As evil as SQL Server is, even if it EATS the entire database and needs 3 days of downtime, it is KNOWN. We know the 3rd party software is written against it 1st, Oracle 2nd, and we know that no matter how many sleepless nights dealing with it happen, there is an end in sight.

We accept that we are not a database development shop, we don't have the skills, nor do we have the time, money or expertise to hire the really bright people and have them add what we need.

There was hope for SAP-DB based on the fact that it seems like it is being actively supported by the commericial entity that owned it before open sourcing, and also the fact it is very Oracle line in it's SQL syntax. But upon reviewing our dependance on the 3rd part app as writing this, even if it was as quick, it would have been a hell of a fight to release it to production. I'd probably run parallel for 6 months, which would cost me a hell of a lot mroe effort than the cost of a few more SQL Server licenses.