I have found a way to download this. HP support simply told me to use the same broken link, which was a bit of a washout.

Having tried various combinations of hardware, OS and browser, including Windoze, I find that Mac OS 9 using NetScape 4.7 will successfully commence the download of this 38Mb of bloatware.

I'd still recommend anyone looking for print drivers to go for gimp-print - their driver is fast and robust. But HP Director remains useful for early warnings of low ink levels. Also, some photos print better with the HP driver.