Earlier quoted context omitted.
They can legally do whatever they want. They've pulled apps before for the same rule. It's part of playing in Apple's ecosystem. As a developer you always take the risk that Apple will decide to wield the ban-hammer, and you basically have no recourse.
Just like Microsoft could legally do what they wanted on windows vis-a-vis Netscape and IE.
Apple is so far from being a monopoly, it’s not even funny.