I have an installer available now for GRASS 6.4rc5 on Snow Leopard. Compilation in source also works.
One change that may affect some: GRASS_PYTHON should now be a path to the 'pythonw' executable variation, not 'python'. Most users should not need to set this and leave GRASS_PYTHON unset.
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William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/
All generalizations are dangerous, even this one.