Fiber optics with small nicks in the run works pretty well, having everything lead back to a single LED. There was an iBook one done this way that did, as you mention, tie into the backlight inverter, which had the bonus of dimming it (though tied to the screen...).

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Something's not quite right here. A backlight inverter produces hundreds of volts (the better part of a kV, in fact) at low current. LEDs operate with a couple of volts at 10s of mA, say. If the iBook project was tied to the B/L inverter, the keyboard light was most likely CCFL-based as well (unless its particular inverter module has additional, low-voltage outputs that are not found in conventional modules).