It’s a research dataset, similar to MNIST or CIFAR. Stanford does not want to be in the business of monetizing patient data, so it restricts commercial use.
Often sources of this type of medical data will give them to universities under the no-commerical-use condition.
It's because if they charge for it the admin of having to pass money back to participating people is prohibitive.
Often you can't buy these datasets at any price.
Then imagine it’s not your unique way to loop over a file in python, but your medical information.