Tested with OS X 10.8.4, Xcode 4.6.2. I haven't played it extensively but it builds and runs.
Not sure if it compiles with older OS/XCode versions. This worked for me, your mileage may vary.
Cataclysm-DDA uses SDL, SDL_ttf, ncurses, and gettext.
SDL can be installed as frameworks or shared libraries.
SDL framework
http://www.libsdl.org/release/SDL-1.2.15.dmg
SDL_image framework
http://www.libsdl.org/projects/SDL_ttf/release/SDL_ttf-2.0.11.dmg
Copy SDL.framework and SDL_ttf.framework to /Library/Frameworks
or /Users/name/Library/Frameworks.
Using a package manager:
Fink, Homebrew,
MacPorts, or pkgsrc.
Install gettext and ncurses. Also install libsdl and libsdl_ttf if you're not using frameworks as above.
Without a package manager, building from source isn't too difficult; follow instructions in the source archives.
From the Cataclysm-DDA source folder:
$ export CXXFLAGS="-I/path/to/include" LDFLAGS="-L/path/to/lib"
This adds search paths to find shared libraries outside of /usr and /usr/local.
Multiple -I/... or -L/... paths can be specified.
$ make NATIVE=osx RELEASE=1 TILES=1 FRAMEWORK=1 OSX_MIN=10.6
$ ./cataclysm
or
$ ./cataclysm-tiles
NATIVE=osx builds for OS X.
RELEASE=1 builds an optimized 'release' version.
TILES=1 builds the SDL version; omit to build the ncurses/console version.
FRAMEWORK=1 uses frameworks; omit for libsdl, libsdl_ttf.
OSX_MIN=version sets -mmacosx-version-min= (mine needs to be 10.6); omit for 10.5.
$ make bindist NATIVE=osx TILES=1
Create a .tar.gz archive of the build; omit TILES=1 for the console version.