One might wonder how they go about obtaining Rackspace Open Cloud specific credentials, which is explained in this document.
Your Rackspace First Generation/Legacy credentials and account will be the same for the Rackspace Open Cloud. Additionally, you can use these same credentials to add both the Rackspace Legacy clouds and Rackspace Open Clouds in the same RightScale account, so there is no need for multiple RightScale accounts to accommodate both cloud platforms.
Keep in mind that the only shared credential required for adding both Legacy and Open Cloud platforms to a RightScale account is the 'username' credential. See the OpenCloud registration tutorial to compare the necessary credentials needed for addition to RightScale.