It would probably be not too difficult to find the macros that generate the index and add in the appropriate PdfTeX instructions to make hyperlinks.

Although, as a veteran Knuth code reader, I would say that his code is intended to be read linearly, like a book, rather than in bits and pieces. (Think of it like dynamic programming: it's more efficient to start from the little functions and work your way up, than to start from the big functions and recurse your way down.)