Premium device vs Premium plan - What are the differences?

All Volumio devices (Primo, Rivo, Integro) or products by Volumio for third parties (e.g. Bladelius, MiniDSP, etc..) come with an onboard premium lifetime plan without the need to subscribe to a paid plan.

This plan is exclusively valid for the product itself and is not transferable to other devices. (e.g. to be able to use multiroom feature)

Devices not branded as Volumio, but on which Volumio can be installed (e.g. RPI), allow access to Volumio FREE or PREMIUM (paid).

The premium plan in question allows access from 6 controller devices simultaneously and the addition of 6 devices to the account. (e.g. to be able to use multiroom feature)