I think Pharo 1.3 and 1.4 (not 2.0) should run ok with Carbon-based VMs. You can get them from:
Let me know if that works.
Considering that 10.5 was released in 2007 and the last(!) update is from 2009 (!!!!),
I am sure that a very old version of Pharo is good enough.
I really don't get why people think that new version of Pharo should run on an OS
that old. And if you can't afford to buy a new machine, I have an advice: Don't buy
Apple, ever. Buy a shitty old Dell laptop (best some from 2007, too) and install Linux.
Problem solved.
Marcus