It took way too long... I had to learn more about IOKit (And especially IOUSBFamily) than I ever wanted...
There were countless kernel panics while developing... But finally here it is:
The XSKey Emulator in a version for OS X is done.
Sadly the simple drag & drop installation like on OS 9 is not possible on OS X.
So this emulator is a kext (Kernel Extension) that simulates a whole USB controller with a XSKey plugged into it.
As for compatibility, it works on 10.3 up to 10.9 on PPC, Intel 32bit & Intel 64bit.
Maybe it also works on 10.10+ but it is unsigned and if I remember correctly kext signing is enforced starting with 10.10.
I tested Logic 5.5, 6.0, 6.4, 7.2 and the SoundDiver 3.1 Beta all working fine for me.
I ask everone who downloads the emulator to let me know if it works correctly for them.
Also please don't distribute it outside this forum for now. I will upload it to the garden for everyone if it
seems to work ok, but I want to "Beta Test" it a bit first.