Other Firebird libraries
For the native SQLDB (the FPC/Lazarus built-in database library), see Firebird. That page also contains some general Firebird-related information
FBLib Firebird Library
FBLib is an open source library, for direct access to Firebird Relational Database from Borland Delphi, Kylix, Free Pascal and Lazarus.
Current features include:
- Direct Access to Firebird 1.0.x 1.5.x, 2.x Classic or SuperServer
- Multi platform [Win32, Gnu/Linux, FreeBSD)
- Automatic select client library 'fbclient' or 'gds32'
- Query with parameters
- Support SQL Dialect 1/3
- LGPL license
- Extract Metadata
- Simple Script Parser
- Only 100-150 KB added into final executable
- Supports BLOB Fields
- Export Data to HTML or SQL Script
- Service manager (backup, restore, fix…)
- Events Alerter
You can download documentation on FBLib's website.
FBLib is no longer maintained by the original authors. As the tiOPF framework uses this library, their maintainers have continued fixing things. It is recommended to use the updated version via svn: 
Please see IBX.
Please see ZeosDBO.