The death of an HD shouldn't be much of a problem: you can make as many backup copies of your key as you want.
Death of the motherboard will be a problem, since each key is bound to one MoBo. Transfer of the key from one dead HW to a new solution will be dealt by the team on a case by case basis. Hopefully they will be around for long: they have been here for the last nine years (MorphOS is (C) 1999-2008) without earning much money, they shouldn't leave us fast! Moreover, they still have fun making MorphOS, as far as I understand.

Kind regards,
Andrea