Hi all, an early version of VTServer is still at: http://www.tuhs.org/Archive/PDP-11/Tools/Tapes/Vtserver/
I think some others took it and extended; Fred van Kempen springs to mind. To load V6, you need to build a virtual tape which replicates the V6 tape. Hopefully this is easy to do. However, the problem is that both "boot" and "vtboot.pdp" contain the client-side code to talk to the server, and it seems that I didn't supply the source code for this. I'll go home and dig through my old stuff and see what I can find. Cheers, Warren