The diff was as easy as adding a new select option for 10.9 version in install.sh, and a little patch fixing com.apple.kpi.libkern version string. Don't forget to install latest libusb, i.e. libusbx in homebrew!
I added a kext for mountain lion to osx.tar.gz and modified install.sh to use the right one or fail if no suitable kext is available.