just starting/flavors of Unix

[GASS at WVNVAXA.WVNET.EDU]

I'm just starting to look into grass.  I've got ISC Unix and Coherent
OS.  Has anyone ported source code to run on either of these two?  I
am also trying to run down an older model Sun to run Grass on.  I know
that some vendors have ported to Mac and I've got a couple of them 
around.  Main thing is I don't have the $1,000 or so for commercial 
versions so need public domain or cheap teweaked version.  Thanks.