Firebird database provider will be part of the next release of Mono 1.1.xx.

FireBird: Carlos Guzmán's Firebird database provider has been checked into CVS and will be part of the next release of Mono 1.1.xx.

Firebird SQL can be used either in server/client mode, or it can be embedded into your application to simplify configuration and deployment of smaller applications. Both modes are supported by Carlos' provider.

from mono blog