If memory serves, the UNIX dialect that they run is SysV release 2.
It's a fairly complete SysV implementation, with a nice, low-overhead
GUI called "UA", for User Agent. There is no networking, but there's a
(rare) Ethernet card for the machine, which was shipped with an IP stack
written by Wollongong. The IP stack ran in short spurts between
crashes, but you could use it to get stuff on or off the machine.
Well there's always Kermit and UUCP - and one could always plug a few serial
ports into a DECserver or something to get "networking" into the device :)
To bring this on-topic for the list, could it run DECnet?
Regards,
Peter Coghlan.