So, thanks to a tip (thanks, Jerry! :-), the source has been found: https://github.com/chapmajs/vtserver/tree/master/pdpvtstand http://www.shiresoft.com/pdp-11/software/ For some reason, the TUHS Archive doesn't contain the later versions of VTServer: http://www.tuhs.org/Archive/Tools/Tapes/Vtserver/ and in those (unlike the earlier versions), the standalone source is in the same archive file as VTServer itself. Noel