I reached out to Sonos the other day about adding Gizmo or JR Remote, this was the reply:
"Thank you for contacting Sonos Customer Care regarding a JRiver Music Server.
Great to hear you're a fan and would like to see this service added to Sonos. We will happily work with any music service provider to deliver their content over Sonos. They can integrate with us using the Sonos Music API. Further information on integration can be found within this link - 'Sonos Music Partners'
We'd recommend reaching out to JRiver directly to share your request and our Music Partner web link.
Moving forward, feel free to reply to this email anytime with any further queries or questions you may have."
Gizmo on Sonos should be available already , why has it not been a priority for JRiver with the proliferation of Sonos?