First of all, admission from the wait list at most schools are very rare. Don’t expect anything would happen. Second, when it happens, you will have a very short time to decide. It is not binding at all. If you do accept the WL admission offer, you need to notify the school you have originally committed and withdraw your enrollment. You are likely to lose your deposit at that school. In any case, you can only commit to one school at any time although a small overlapping due to processing time is not an issue.