On PowerMac B&W G3 400MHz 750 processor 384M RAM, orca does not complete building from ports or packages without the system becoming unresponsive. I've let it sit or a day and went back, nothing was responsive. Testing festival and festvox comes out okay. The old emacspeak port is too Linux dependent to properly work on ppc. KDE gives me static with automatic or sndio as the audio backend.
CURRENT results in crashing on ports and packages, so I've abandoned the idea of using it on a lowend mac. The last 4.8 image I downloaded was a week ago, most up to date version. On gnome, it seems to be a gtk window error. The B&W has been dedicated to another project but, there should be no problem in reinstalling OpenBSD to it.