Hi Lisa!
The codebook isn't being actively maintained by Task Force, which is probably why they took down the link. Nafundi has a fork at https://github.com/nafundi/odk-codebook that we plan on upgrading soon.
Until then, I happen to have a copy of Task Force's version at https://nafundi.com/downloads/Task-Force-LINKS-Codebook-v1.1.zip that you can try. If this solves your problem, click on the ... and click on the checkbox to mark this issue solved.
Oh and when you get a chance, please introduce yourself here!