> What is the earliest version of Firebird that the current Jaybird driver supports?

General rule: new Jaybird release is tested against current version of
Firebird.

Tested means that all JUnit test cases (~450 test cases) are run for
each JDK version - at the moment it is 4 x 450 test runs.

On the other hand, we try to maintain the compatibility with all
previous version - any compatibility breakage is usually discussed here.

For example, in Jaybird 2.0.x we dropped support for InterBase 6.0 and,
possibly, Firebird 0.9 due to one flag that we need to determine the
Firebird server version to be able to execute correct metadata queries.
The only possible way to keep support for IB 6.0 was to execute call
twice - one with flag, and in case or error - without it. It was
considered as too ugly.

Same with JDK 1.3.x and 1.4.x support in upcoming release - issue was
discussed here before the decision is made.

But it always can happen that some new feature conflicts with some very
old Firebird version. Issues with newer FB versions are usually detected
during beta test run.

> Does it work
> out of the box with all official releases of Firebird (from 1.0 on)?

I would suspect that Firebird 1.0 (how many years since its release? 5
or 6?) might have some compatibility issues, but basic functionality
should work. Or you just take Jaybird 1.5.6 which definitely supports
Firebird 1.0.

But in general it is very easy to find out - just take the sources and
run the test suite against the desired version of Firebird server. If
some test cases fail, check whether you can live with those issues and
make your decision.

Roman