If you wonder how Firebird 2.1.3 stable can be compiled on Freebsd 8.1 wonder no more , Here is the thread with patches and instructions needed .
He does have some nice tutorials on the website with Freepascal and extJS
Damyan submited the patches to make Firebird 2.5 buildable on FreeBSD.
You can watch Debian building logs here
You can install firebird 2.0.x on these new ports for debian : kfreebsd-amd64 kfreebsd-i386 powerpc sparc