I know this is a bit of a necro bump but I did release the "cemetech"(as Kerm so happily dubbed it) GCC PrizmSDK-0.2 a while back and would love to help anyone get it setup if needed.
As for using it on Mac OS X you would need to install xcode and then compile and install a gcc targetting the superh series processors. If you want I can help walk you through the process any time, just hop on irc, or use the chat box, and highlight me. You would just need some parts of my sdk and I have all those individual files available for download.
As to keeping this on par with Simons work I would really love to work with him on standardizing things a bit. I'm fine with the automated syscall generating and have written a script to duplicate its work for use with my SDK but the biggest issues I have are with the header and helper functions organization. As it stands right now you can't easily use the headers from one SDK with another or even reliably compile code written with one on another.
I'd like to fix that so that it is easier for the end users of either SDK to adapt them to their needs.
My first issue is the lack of clarity on whether or not C++ is really supported and why some headers and source files use hpp/cpp instead of h/c. IMO we should keep the SDK's and their API's pure C and leave it up to the users as to whether they want to use C or C++. Many of your headers are already encased in Extern "C" {} so why even bother having them use the .hpp extension?
My second issue also relates to the headers and it is the fact that you mix equates and structs used by syscalls with custom functions you have added. This increase the amount of work for me greatly and adds to user confusion because they can't tell what is a syscall and what is something you added to the SDK yourself.
My last issue is that darn chm file.

Yes its nice that there is some documentation but damn is it a pain in the arse to find any of it in there. Omnimaga was kind enough to host the prizmwiki at
http://prizmwiki.omnimaga.org we should use it. I have been trying to update it with some of the things I have found but its just not all that useful as it currently stands. I think the first step would be to start getting the syscalls on there. The documentation for them is scattered about this forum, your .chm file and our heads. Getting on in a centralized location would help everyone move forward and allow one to much easier find the information they need.