Subject Review of 'SQuirreL SQL Client'
Author marius popa
Mention of Firebird jdbc driver

"Adding a new driver, for Firebird for example, is a simple case of
selecting New Driver from the menu, entering the path of the driver Jar
file, entering a sample URL and it's done. To connect to an actual
database is just as simple. Select 'Add New' from the Alias menu, select
the driver, enter the database URL (including the user name) and that's it."

Marius - Linux admin