FluidSynth for Max/MSP
The FluidSynth SoundFont synthesizer is written by Peter Hanappe, Josh Green et al. and freely distributed under the Lesser GNU Public Licence (LGPL).
Please refer to http://www.fluidsynth.org/ for further information about the FluidSynth project and SoundFonts.
The Max/MSP external fluidsynth~ is completely based on the code of FluidSynth and developed by Norbert Schnell (which was thanks to the fluid, complete and well organized API provided for FluidSynth really not a big deal) with the helpful advice of Roland Cahen.
The fluidsynth~ external is as free and LGPL as FluidSynth. You can find the sources as part of the FluidSynth Savannah project.