I was getting a little impatient for QGIS 0.8, and decided to build from SVN. Universal binary for both PPC and Intel Macs. Definitely works on Tiger, but I haven't tried Panther yet - depends on Qt and QGIS, since my other packages should work on Panther.
GRASS reading support is provided by GIS Libs. GRASS editing requires a full GRASS install, but I haven't gotten that far yet, so don't ask me what to do. Eventually I'll probably make my own GRASS installer and make sure it works with QGIS. It may be a simple thing and you could use any GRASS installation.
I've been working on streamlining the build process on my MacBook, and I have a fix for the non-working Python MapScript, plus some minor package updates, I just got distracted by QGIS. Look for more soon.