No. You should only ever have 1 username and 1 password. It is actually a violation of our terms of service to have more than 1 username or password with our system. Having 1 username and password will get you access to all the information you need for any organization with our systems. You can manage 1 availability calendar or multiple availability calendars - that's up to you. Some users like to manage just 1 calendar for all their organizations. However, some users like to have different calendars for different organizations.