The title here isn't very good. He was previously sentenced to 13 years in BC, which was then replaced with a 6 year sentence in accordance with Dutch law.
I personally take the stance that the justice system should be rehabilitative above all else, but I honestly don't see how someone like this can be rehabilitated. No normal person would be capable of committing such an unambiguously evil act, and it's a shame he can't be put away for life.