You can add as many collaborators to your account as you'd like - they just need to make an account at https://intrinio.com/signup.
Once they have an account, you can add them to your account (https://intrinio.com/account/access_keys). It looks like this from your account page:
Once you add the email they signed up with, they will see a specific set of collaborator access keys on their own account page that they can use and their usage will be counted against your subscription.
Their API key will include their username but the password of the primary account.
This allows a single paid subscription to be used with any number of developers, analysts, or employees.
If you can't find your API keys, start here.