I know you posted a long time ago, but I would like to understand more of your question. Could you provide additional information about what you are trying to do with the user info? Put into a form? Add as a person value and control? Thanks,
there shouldn't be a need to do any transfer of credentials. If your Nintex Live form is not set to anonymous, then they can login with their corporate credentials.
That, or they can set up a Windows Live account that maps to their corporate email address and use Windows Live to do the authentication.