Ghostscript is a PostScript code reader and interpreter for Mac computers. The software is open-source and free, but installing it requires a bit more work than other programs need. In addition to downloading the requisite files, you have to use Apple's Terminal program to configure the software to work with your computer.
Download the latest Ghostscript software under "GPL Ghostscript" at the link in Resources. As of May 2011, the latest version is 9.02.
Open the file that downloads. It will extract a folder onto your desktop named "ghostscript-xxx."
Open "Terminal" from Mac's "Applications" folder.
Type "cd" followed by a space.
Drag and drop the "ghostscript-xxx" folder from the desktop onto the Terminal window. A list of files and commands will appear.
Type "% ./configure" (no quotes) and hit Enter.
Type "% /make" (no quotes) and hit Enter.
Type "% /sudo make install" (no quotes) and hit Enter.
Restart your computer. Ghostscript is now installed and configured in your "Applications" folder.