The unsatisfying practical answer: No company whose business relies on their website is going to be comfortable assuming the answer is no. So "commercial" usage

The unsatisfying practical answer: No company whose business relies on their website is going to be comfortable assuming the answer is no. So "commercial" usage, where "commercial" is defined as "worth suing and has lawyers who are worried about being sued," needs to buy a license, and "personal" usage, which is the complement of that, doesn't.