has anybody encountered this and fixed it?
when i open it, the screen blanks briefly and then the game crashes.
i'm running OS X 10.11.5 and have a 15" macbook pro

Did you find solution?

Run in Terminal. It will spill out the reasons. By the way, on Linux I moved away a few libraries and used systemwide newer ones. Perhaps this can be relevant.

libmikmod.so
libogg.so
openal.so
libpng12.so
libSDL-1.2.so
libSDL_mixer-1.2.so
libvorbis.so

each if them has ".0" link and ".$version" actual file, with ".0" pointing to the actual version.
all these files were installed using system package management and present in the system.

Difference? Sound is no more choppy and game does not lag anymore.

In addition, if Mac changed how OpenGL works, you may need either to play with OpenGL libraries or ask support staff/Introversion for solution - because that would require patching and recompilation.

One possible cause for it crashing on opening is mods. My workaround for this type of crash is to run the game with no mods.