Apenas tentei isso no meu MBP de 2013 com 10.8.5:
O teclado externo ainda funciona bem e eu pude desativar e reativar meu teclado interno.
Para desativar o teclado interno de um Mac portátil:
sudo kextunload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTCKeyboard.kext/
The internal keyboard is then disabled, external keyboards will still work.
Para reativar o teclado interno de um Mac portátil:
sudo kextload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTCKeyboard.kext/
Quando inicialmente desabilito o teclado interno, o terminal notifica-me que:
(kernel) Can't unload kext com.apple.driver.AppleUSBTCKeyboard; classes have instances:
(kernel) Kext com.apple.driver.AppleUSBTCKeyboard class AppleUSBTCKeyboard has 11 instances.
Failed to unload com.apple.driver.AppleUSBTCKeyboard - (libkern/kext) kext is in use or retained (cannot unload).
No entanto, o comando funciona, sem efeitos negativos.
Agradecimentos a: macrumours