While not being an expert, I'd like to add my thoughts to this discussion:
I really think that such multi-session functionality must be in the realm of a seperate application/tool, and not something that should be considered for inclusion in VNC (although it might be the case that the right people for making such a tool would be the UVNC developers. It might also be the case that such a tool would benefit from some kind of support in UVNC and vice-versa.)
The reason for this position is that (U)VNC is a tool/protocol for transfering the desktop input/output (in the sense: "What you would see/do if in front of the machine"), and as such have nothing to do with what is actually appearing on the display (ie. UVNC does not need to know anything about which account you are using and so on.)
I'm therfore guessing that such multi-session support would require VNC to be (almost) entirely re-written.
On the other hand, I can well see the many good reasons for such multi-session capabilites. I would therefore suggest that those needing such capabilities try to lobby for the production (by the UVNC team or..?) of a seperate tool for this. Preferably one that would allow easy "integration" ("cooperation" perhaps?) with UVNC.
I imagine such a tool would handle all the multi-session specifics (and/or hook up with existing solutions such as the one mentioned in this thread, of which I know nothing though?) And simply provide some (more or less clever) means for UVNC to "connect" directly with an individual "session" (and, of course, allowing the viewer-user to specify which session that should be).
But who knows, it is entirely possible that such a tool already exists, in which case the thing to do would be to lobby for an effort to ensure easy integration of that tool with UVNC.
Some further ramblings about this topic:
I think it would be VERY nice, if it became possible to do build something similar to your typical "Windows Terminal Server" setup, only without the expensive software and (some) freedom of OS choice. One could even imagine improved performance over the M$ solution (wouldn't be the first time).
With the availability of dedicated (thin/hardware) VNC clients (see www.axel.com
), it is intirely possible to imagine a setup with a centralised (cluster of) server(s) providing multiple sessions to a number of such "thin" hardware clients through the VNC protocol. Probably a much cheaper (and possibly better?) solution than buing an existing, say IBM's, Terminal-server hardware solution.
I for one will be keeping an eye on how this develops (even if I have little personal use for such a "terminal-server" setup).