Mac OS X 10.3 Server has the option of formatting a mac hard disk with a case-sensitive variant of HFS+, known as HFSX. (Details at Apple.) This filesystem variant has proven to be useful while doing Unix-ish development in the Mac OS. (Anyone ever tried to call a source directory "cvs" while using Mac OS? Good times...)
Unfortunately, since HFSX uses a different magic number in the volume header ("HX" instead of "H+"), the hfsplus filesystem modules do not recognize case-sensitive HFS+ partitions as being valid. (Mount, for instance, will give a standard "bad superblock" error message.)
Does anyone know if the current utilities support HFSX? I have not found any obvious commands, switches, options, etc., but obviously, I might have overlooked something. If not, are there any plans amongst the HFS+ developers to support this? I have no experience with the details of the hfsplus kernel module, any of the other HFS+ utilities, or of the guts of the HFS+/HFSX filesystem format itself. So, I have no idea if this would be a major undertaking or not.
If this is not an urgent task, the easy and tedious solution would of course be to reformat the Mac OS partition as a standard case-insensitive HFS+ filesystem. In this case, maybe a notice could be put somewhere in the Gentoo PPC FAQ's mentioning that HFSX is not yet supported?
--doug

