I checked with Jazz radio.com and received this reply, to my surprise:
Hi Brian,
Thank you for contacting us.
You can use your Premium subscription on multiple devices, but not at the same time.
Please note that Premium streaming is limited to 1 active connection at a time per our TOS (terms of service).
If you have multiple active connections, our system will block additional connections.
Thank you for understanding.
Let us know if you have any additional questions or feedback.
Kind regards,
Pavle Popović
Customer Support