Their only restrictions on membership are listed on their websites. There’s even a contact form if you want to join.
Basically you need to be a man (OK, I know that’s a bit crappy in this day and age), with a belief in a higher being, what that is can be whatever, and be a decent person, unlikely to screw folks over for your own gain.
Their whole ethos is to make a person the best person they can be, to be selfless and to strive to help others where you can.
As I said, I’m not one, never have been, never been inclined to become one, but if I did have those thoughts, I’d have no doubt that I’d be accepted into their ranks, simply by contacting my local lodge and talking to them about what’s expected of me by doing so.