Well, as somebody who has followed Knuth's activities off and on for nearly 30 years now, I'm pretty sure the latter was meant. That man's put out enough good work for three or four careers of us meer mortals.
If you are asking does the English grammar of the sentence imply one or the other, or is it ambiguous, the answer is that it is indeed ambiguous.
I don't think that there's a really good way to restructure that sentence with commas or hypens or whatever that will resolve this and not look more awkward. I'd suggest the author do one of two things:
- Provide enough context in surrounding sentences that the meaning is obvious. Mentioning the extreme length of his career in the previous sentence is probably sufficient.
- Remove the word "original". I does provide a wee bit of value to that sentence, but I think its implied (and with only the proper meaning) if you remove it.