There is this steps in the Firebird quick start guide:

3. copy the interbase.msg file to /opt/interbase

4. In system-wide default shell profile or using setenv() form a shell
create the INTERBASE enviroment variable and point it to
/opt/interbase to enable API routines to locate the messages.

This is really necessary? I alredy install my program in a client
justing putting the libgds.so and libgds.so.0 in the /lib .