The article is pure bunk - none of these questions are illegal. Discrimination based on on answers to these questions is illegal, but not asking them.
As an interviewer, these are questions which should never be asked, because they leave you open to an accusation of discrimination. That doesn't make them illegal.
Comprehensive discussion and advice on the topic: http://www.manager-tools.com/2011/06/answering-illegal-interview-questions-part-1