> Does anybody know a free program to maintain a Firebird DB data
> dictionary ?

What exactly do you mean by that?

Create/edit/drop tables? Sure, the "isql" command line tool that
comes with Firebird is free.

Martijn Tonies
Database Workbench - development tool for Firebird and more!
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
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