since v2.5 it is possible to use Firebird embedded without install of full CS package.
All you need is to create the almost the same folders layout as with full Firebird package, including bin, intl, lib, plugin, UDF folders and its contents.
Create simlink lib/libfbembed.so.2.5 pointing to the lib/libfbembed.so.2.5.2
Remove not needed binaries from bin folder, if necessary
Set FIREBIRD to the root folder.
Set LD_LIBRARY_PATH to the lib folder (not to the root !)