It's similar to before. When I launch the "HP Printer Selector" it can find no printer, and when I just try to add a new printer for printing a document, having chosen "HP Jet Direct – Socket" and "General Postscript" it just says "Network host '10.241.191.1' is busy; will retry in .. seconds."
After having posted I found a very extensive thread on a similar subject, dealing with the fact that AppleTalk apparently is no longer functional under SnowLeopard, so that you may have to connect by IP address instead. I have only browsed through part of it, but one thing that was suggested there was that the IP address of the printer must not be too different from that of the computer. This indeed may be so in my case. Maybe I should have studied previous discussions better before posting.
By the way, the configuration page of the printer states that AppleTalk is disabled.
Finally, what I really aim to do is later to connect this printer to an Ethernet router (which is in another place) rather than directly. Maybe I should skip this exercise and take it from there instead. I really just wanted to make sure that the JetDirect card, which I have purchased, actually works, and I take it that it does.