> Is there a Jaybird branch that can be used with Firebird2?

There is no special branch for Firebird 2.

As far as I know, Firebird 2 does not change the wire protocol or the public
API. Also I'm not aware of any extension of Firebird 2 that would require
changes in driver (but if you have one, please post them here).

So, JayBird 1.5.x should work with Firebird 2.

Roman