FWIW, I seem to have built bash3 at some point for A/UX, binaries here
I haven't fired up my A/UX machine in a while, and I can't remember whether it had proper signal handling, job handling, and whether it was built with readline functionality. It should have been enough to handle autoconf scripts though. Using bash with it's builtins is usually both faster and more reliable for running autoconf and gnulibtool scripts than the default /bin/sh on A/UX in my experience.
Also, get it while you can, I'm not sure what I'm going to do with all that stuff when iDisk goes away...
I used to use tcsh religiously, but about a decade ago I had to spend more time than I wanted fixing bugs in its interrupt handling code. After spending enough time to familiarize myself with its internals, I decided it was time to move away. An unknown evil is sometimes preferable to a known evil, I guess.