You can install it from sources. Here's a recipe you might try:
0) Install Xcode + "Unix Development" a) Get the Xcode .dmg from http://connect.apple.com. You'll need to join the site first; it's free for the "online" membership which is all you need to get Xcode. Look under the "Developer tools" section in the downloads pane. -- For Tiger (10.4), you'll want Xcode version 2.5 -- For Leopord (10.5), you'll want Xcode version 3.1.3 -- For Snow Leopard (10.6), you'll want Xcode version 3.2.2 b) Open the .dmg and run the installer c) On the "installation type" pane, click the "customize" button and make sure the "Command Line Support" option is checked d) Click through and let the installer run e) Unmount the Xcode .dmg 1) Install X11 a) Find your install disks and run your installer. In the "optional installs" section, you should find an option to install X11. b) Optionally, you may find the X11 download from http://support.apple.com Unfortunatly, it is difficult to directly link to the page you need, so search for "X11" in the support section to find the download you need. c) Run the installer, etc. 2) Install MacPorts a) Go to http://www.macports.org/install.php and get the right dmg for your version of OS X. The links are near the top of the page under the heading "Installing MacPorts" b) Run the installer, etc. 3) Start X11 If you previously started X11, shut it down and restart it. This should open an xterm window. If not select "Applications -> Terminal" to open one. Use this window to enter the commands in the following steps. 4) type: which port It should reply "/opt/local/bin/port" If not, type: source ~/.profile then try again. 5) type: sudo port sync It will ask for your password. The following steps may also ask for your password, depending on how long the delay is between typing them. 6) type: sudo port install ocaml 7) type: sudo port install camlp5 use_parallel_build=no 8) type: sudo port install gtk-doc 9) type: sudo port install lablgtk2 10) type: sudo port install coq +coqide 11) type: /opt/local/bin/coqide & Note: you may have success with skipping steps 6-9 and just executing step 10 directly. In theory, this is how it is supposed to work. I have had problems in the past which required steps 6-9 as workarounds. Your mileage may vary. Double note: with some configurations, coq will fail to build correctly because of an old (< 3.81) version of make. If your coq build fails and the log file indicates that the configure step failed when checking make versions, you may have to upgrade you version of make.