to build and use softcut_jack_osc on macOS, JACK must be installed and running. also some packages dependencies need to be installed via macports or homebrew:
sudo port install jack
sudo port install libsndfile1-dev
sudo port install liblo
to use the software, jackd must be running:
jackd -d coreaudio
and the selected audio device must have at least 2 channels of I/O. (i find it easiest to use an aggregate device on mac laptops.)