Thanks - that was my original conclusion / fear, although I've been wrong before..... I'm using the term "zone" to mean a physical player / renderer controlled by MC and delivering (i.e. playing) content from the main library. JRemote seems to me to be the client and the controller simultaneously when set to play on "this device". If it's not, what is the client - the iPhone's music player?
Similarly, if WebGizmo is not also the client on my Chromebox, what is? a default music player installed with the OS package?
well semantics, if you use the more or less common terms for digital playback -- you have a media server, a media renderer, and a control point.
Each JRiver install can be all three. Usually you have only one computer on your network acting as the media "server" (do not confuse a NAS a the
media server). A "Client" (a machine having a full JRiver install) is,
usually, only a renderer and a control point. Each machine, with some exceptions due to the OS, has complete functionality - including the option to see the "server" machine's local zones which can then be controlled. Some things like importing, cover art, file moving etc. can only be done on the server machine)
Then you have "DLNA" devices that can be accessed by your network and used as renderers. Zones are local configurations, clients can see zones on machines acting as media servers. As such they can be seen on control points and music can be sent to them (or pulled). As such, again, these zones can be "physically" separate.
So, unless you have multiple PCs (or mac or Linux machines running JRiver in the network) you don't have any "clients". I'd say JRremote and WebGizmo are just controllers with the ability to be renderers like other DLNA devices.
Now this is just Arindelle's definitions of a JRiver network
... so if you just take the Wikipedia definition literally, client can mean just about anything accessing a server's data on a network. So once again ... semantics