<<I've managed to solve it by patching the libEngine12.dylib file in plugins directory, as well as setting the DYLD_LIBRARY_PATH to the application directory.


install_name_tool -change /Library/Frameworks/Firebird.framework/Versions/A/Firebird @executable_path/libfbclient.dylib plugins/libEngine12.dylib

export DYLD_LIBRARY_PATH=$(pwd)>>

Yes, by default we build and install as a Framework on MacOS, which means
as part of the build process we finesse the locations of all the relevant libraries and
executables etc using the install_name_tool. If you look at the source code specifically
posix/postfix.darwin, and you will need to do the same for all the libs/executables
you wish to use...

There was a script to do this in Firebird 2.x
See posix/builds/install/arch-specific/darwin/embed.darwin

Paul