libusb is setup to be used locally! 
this means it is linked to the app and you don't need to have libusb install in /usr/local/lib

the file usb-1.0.a is what is being linked in the xcode project. 

this is because xcode is stupid and if you try and link libusb-1.0.a it freaks out and looks for dylibs in /usr/local/lib

usb-1.0.a is a local copy of libusb-1.0.a

to update the libusb:

1) unzip libusb-theo-modded.zip
2) make any changes you need to ( most likely in libusb/os/darwin_usb.c ) 
3) in a terminal in the root libusb-theo-modded/ do:
make clean
./configure
make 

4) now there is an invisible folder called libusb-theo-modded/libusb/.libs/
5) copy the contents of this folder to libfreenect-modded-osx/libfreenect/libusb-osx/libs/
6) now copy the libusb-1.0.a to usb-1.0.a 

xcode should now be using your updated libusb!
