Although several reader are successfully running Mac OS X Server on their PowerBooks (link), one reader reports major difficulty running Darwin on a Wallstreet/250:
After several hours and several attempts (One involving a full core dump) I have been unable to get the current 0.2 release of the Darwin OS to run on my wallstreet 250; It gets to the end of the startup sequence and then hangs. This seems very odd considering that this is the core foundation of Mac OS X Server, which other people have successfully installed onto other powerbooks.