It means people who allow themselves to use it since many people have personal rules against it. People who may use it means people who are allowed to, and the only ones who aren't allowed to, unless they live in China, are usually the ones who have a personal rule for themselves that keeps them from using Google services. This is of no use to people boycotting Google that's why my choice of words may seem confusing, unless they don't. No need for an English lesson as long as you can get the main point or spirt of the argument or explain the concept then specific words and details are irrelevant.