Let me see if I can call AndrewFG's attention to this thread... hold tight a day or two.
Got it :-)
Logitech's Media Server (previously known as Squeezebox Server) has two functions: 1) it hosts your music library, and 2) it sends music to your Squeeze players. LMS implementation of both these functions uses proprietary processes, formats and interfaces.
If you add a "UPnP/DLNA front end" to LMS/SBS you can make it do two new things:
1) Put a UPnP wrapper around the LMS proprietary music library so that it also appears to UPnP Control Points as a UPnP Digital Media Server (DMS) a.k.a. "ContentDirectory"
2) Put a UPnP wrapper around the Squeeze players so that they also appear to UPnP Control Points as a Digital Media Renderer DMR a.k.a. "PlayTo"
MC supports DMS ContentDirectories to appear as music libraries; and it also supports DMR players to appear as players. With these two features, you can play FROM either MCs native library or from a DMS ContentDirectory, TO an MC native player or to a DMR. Any combination of FROM and TO is possible.
There are currently two "UPnP/DLNA front ends" for LMS/SBS -- namely Logitech's own DLNA plug in (shipped in LMS v7.7) and Whitebear. Frankly Logitech's own plug in is rather rudimentary and buggy (it only supports mp3, it provides very little track metadata on the Squeeze player display, and is very much "Logicentric"...) -- so (naturally) I recommend the 'Bear ;-)
The current public release (v2.2) of Whitebear still has quite a few niggles in its interworking with MC. But in the last few weeks, bob (JRiver) and I (assisted kindly by MrC) have been working closely to improve the interworking and integration between MC and Whitebear. We are pretty close to having finalised all issues, and I expect to release Whitebear v2.3 publicly within the next few days. (If you can't wait, please send me a PM and I will send you a link where you can get a pre-release...)
As MrC says, you just need to install Whitebear on the computer where LMS is running. The rest is more-or-less automatic.
Note: that it is not absolutely necessary, but I do recommend to disable LMS own DLNA plug in. It will avoid excess load on your PC cpu and network. And prevents the confusion of your Squeeze library and players showing up twice in MC i.e. once hosted by Whitebear, and once hosted by LMS own plug in...