rclient work very well on OS X, but you will need some tweak. You could also uses Terminal services via TSAC, or run an x86 emulation then terminal services. Terminal services work verywell though emulation even on a G3 lappy with 128 megs of ram.
The best thing you can do is built an xserver & run thin clients on old 486 & pentiums that is much easyer to config than MS Terminal services & TCAL.