No, you are not obligated in any way. What you decide to do with that knowledge is up to you.
Do you see signs that the student is trying to obey Jesus’ commandments? Most important, does he want to become one of Jehovah’s Witnesses?
From the same WT is the rest of the quote: ". . .continuing to study with him would be like trying to give swimming lessons to someone who does not want to get wet! If the student . . . is not willing to make changes (Get baptized as a JW), why continue studying with him?
So YES, if someone "studies" with the JW's it is most definitely expected, if not demanded that they become a JW themselves.