Much of the base system of Arc expects some Unixisms. In fact, much of the base system of PG's original ArcN expects a mostly BSDisms, and it's really the Anarki fork which supports mostly Linux.
As an example, much of the code assumes that the path separator character is "/", but I gather from mzscheme documentation that Mac OS uses ":". Also, bits and pieces of the Arc system use /dev/urandom.
So mostly I suspect the problems you encounter(ed) are from Arc's assumption of Unix-likeness which might not be available on OS X (not sure however; I don't have access to a real Mac)
Edit: Oh and yes: the first thing you want to do is switch to Anarki, which is more likely to work on a random, non-PG system.
OS X is based on BSD. As for the path thing, wow, that threw me. Not sure what that might apply to. Here's are my PATH entries on a SuSE box and my Macbook, respectively. They're both POSIX compliant.
I guess, for starters, I need to figure out how to set up BIND to route news.localhost to a local directory, and figure out which directories the various bits of MzScheme and Arc should be applied to. My biggest frustation right now is figuring out the syntax for BIND.
Windows internally implicitly supports / as an alias of \.
Note that Arc provides its own http-server which is not very directory-based (rather, something like http://example.com/login would be defined with a (defop login ....) form in the running Arc process), so I'm not sure why you're routing to a directory.
The deal with path separators has to do with the difference between the classic Mac OS (9 and lower) and Mac OS X. Classic Macs used their own path system, which used :s as the path separator (e.g., ":Macintosh HD:Documents:Arc:tut.txt"). When the switch to OS X came, suddenly everything was based on Unix, so file paths became sane (e.g., "/Users/username/Documents/Arc/tut.txt" or even "~/Documents/Arc/tut.txt"). Nevertheless, in the name of backwards compatibility, many things still display paths in the old format, the GUI pretends that :s in file names are actually /s, and AppleScript deals natively with old-style filenames.
Re Anarki: yes, I've found arc2 doesn't work out of the box on CentOS 5, and my repos are botched (something to do with installing PHP 5 during initial install, I think, was what forced me to change something in the repos), so I need to fix the repos to install Git so then I can install Anarki.
