In case anyone has this same problem, I figured it out. The actual “raw” Python notebooks are stored in a different place on Github. You can access it by first clicking on the notebook (which will open it in your browser), then right-clicking “Raw”, and selecting Copy Link Address. Here it is for lesson 1:
https://github.com/fastai/courses/raw/master/deeplearning1/nbs/lesson1.ipynb
The only difference in the address is that the “tree” folder is switched to “raw.”
Enjoy!