First, for purposes of the exam, I want you to remove the word “Realtor” from your vocabulary. Realtor is a trademarked status that you get when you become a member of the National Association of Realtors, which is a private association and there is no legal requirement to join. Therefore, you will never be tested on Realtor related issues. If you are, the answer of “Realtor” will be the wrong answer.
So, as a result, the law is the same way. No where in the law does it say a Realtor has to be at an open house. But it does say that a licensee has to be present at an open house. So, to answer your question, a non-licensed assistant cannot conduct an open house by themselves. A licensed sales agent must also be present at the open house. That’s because an open house is one aspect of practicing real estate, and you need a real estate license to practice real estate.