What they've done is define a property, tack the name "free will" onto it because it resembles some people's definitions of free will, and prove some things abo

What they've done is define a property, tack the name "free will" onto it because it resembles some people's definitions of free will, and prove some things about it. If their math is sound, then good for them. Whether this is applicable to anything is certainly up for discussion, of course.