Please read the copyright for Arc.

Arc does not run on a Macintosh as a standard Macintosh program with System X. Mac users have three choices:

• If you have a Windows emulator, or if you have Parallels Desktop on an Intel Mac, www.parallels.com, you can install and run the Windows version of Arc on your Mac.
• If you have an older Mac with System 9, or an earlier version of System X that supports "classic" mode, you can use the installer Arc1.06Installer.sit.
• If you are a brave soul, you may be able to install Arc as a Linux program on your Mac. Here are instructions.