This week, the Firebird project has finally released version 2.0 final.
Although this version comes with lots of improvements and changes, I think that dbdesc should be able to document 2.0 databases without problems. I will try to find time this very weekend to test it.
Here are the release notes and download page.
UPDATE: Even though you can connect with a Firebird 2.0 server to document a database, using the local (embedded) connection does not work because it needs the new fbembed.dll version. I’ve uploaded a maintenance release (2.0.1) to address this issue. Installer size has grown a little (~1 MB) because of the updated Firebird libraries.