Where is Firebird 2 on Ubuntu and Debian?
When only Firebird 1.0 and 1.5 were available, the Ubuntu and Debian packagers decided to build package for Firebird 1.5, but called it 'firebird2' to avoid confusion with just 'firebird' package. Firebird 1.5 was meant to be a migration to Firebird 2 anyway.
However, when Firebird 2.0 came out, it started to be a source of endless confusion. Since some time Debian packages of Firebird 2.0.x are available for the "unstable" and "testing" suites via the normal Debian mirror network. Backported packages for Etch are available via backports.org.
http://packages.debian.org/source/firebird2.0
For classic get "firebird2.0-classic", for super - "firebird2.0-super".
All the other needed packages will be pulled via dependencies.
For using the etch stable backports read this reference
http://backports.org/dokuwiki/doku.php?id=instructions
Also, Firebird2.0 packages will be availalable in Ubuntu Gutsy:
http://packages.ubuntu.com/cgi-bin/search_packages.pl?keywords=firebird2.0&searchon=names&subword=1&version=gutsy&release=all
And here's a howto for Hardy:
https://help.ubuntu.com/community/Firebird2.1