Bob,
I just tried sdcc 3.1 with a S08js16.
For the JS16 the compile line should contain -mhc08 --data-loc 0x80 --code-loc 0xC400 --stack-loc 0x027F
interesting enough the stack-loc must be in the compile stage (not the linker as it does nothing there).
For flashing, it is likely you can port usbdm without much effort (based on wxwidgets and libusb which are both available on mac).