My eee 901 is now running MacOS X 10.5.6.
Many thanks to the various people out on the web who’ve written up instructions and advice on how to achieve this. The main link I used was this one from Gregory Cohen.
It would be fair to say that the resulting Mac is not flawless - WiFi support is a bit clunky, and there a number of minor things that don’t work right by all accounts (although I’ve yet to encounter any major problems).
That said, this is the cheapest Mac I’ve ever had - and yet I would gladly have paid two or three times as much for a really well put together machine of a similar size, made by Apple. Hint hint.