From the USMLEWorld website:
You are not allowed to sublicense, assign, share, sell, rent, lease, or otherwise transfer your right to use the Licensed Materials. All accounts at USMLEWORLD are monitored for multiple logons. In the event that USMLEWORLD believes in its sole discretion that an account is being used by multiple users at the same time, USMLEWORLD reserves the right to terminate that account without any notice or refund. We also retain the right to sue on grounds of breach of contract. Therefore, please do not disclose your account details to anyone else.