What is the effort to migrate from Blackfish to Firebird ?
I use DBX4
No stored procedure, or function or views
I access all my data trough SQL queries
There is a driver for delphi and dbx4 firebird http://sites.google.com/site/dbxfirebird/
my guess is that is easy for you to dump the blackfish tables into csv and then to import them in firebird and later modify only the application to access the firebird db using the dbx4 firebird settings