Whenever you want to use our APIs in order to go to production you need to first build and test your app in the sandbox, then emulate enough of a usage pattern that approximates your production level usage and allow us to monitor your app, then you would request a production key from us.
Could you tell us more about what exactly you are trying to do from Salesforce?
Yes - it looks like the only SMS function is from the softphone. I am going to want to send SMS's from a Salesforce Contact record. I thought that I would just build an embedded visualforce page in Salesforce, and call the SMS API's to my RingCental account. Just working through the oAuth connection code now.