>> I have the rexx libs in sys:libs like I should as well.

> did you copy the proper Arexx library to the G5

I think he did. At least that's what he wrote.

> or is that no longer necessary?

It is.

> I [...] seem to remember some discussion that a solution which would
> eliminate the need to copy the Arexx library from any AmigaOS3.1 to 3.9
> installation media to a new MorphOS system

If you mean this, it doesn't work with existing ARexx scripts. And the ARexx library based on Regina Rexx didn't come to fruition.