For those that have direct-linked here from download sites, these are the OS X installers. The main GRASS site is http://grass.osgeo.org/.

• Download GRASS.app 6.4 RC5-3 (Leopard) [62.0 MB].
• Download GRASS.app 6.4 RC5-3 (Tiger) [45.0 MB].
• Download GRASS 6.4 RC5 source [20.1 MB].
• Download GRASS.app 6.3.0-3 (Leopard) [24.4 MB].
• Download GRASS.app 6.3.0-3 (Tiger) [24.1 MB].
• Download GRASS 6.3.0 source [16.9 MB].
• R statistics (optional)

NOTE: if you have problems updating, trash the GRASS installer receipt in /Library/Receipts and trash the GRASS application. Then try installing again.

GRASS requires the SQLite3, FFTW3, FreeType, UnixImageIO, PROJ, GEOS, and GDAL Unix Compatibility Frameworks (GRASS 6.3 requires GDAL 1.5, GRASS 6.4 → GDAL 1.6). The installer does NOT check for these, so make sure they are installed before trying to run GRASS. GRASS is Universal for PPC and Intel Macs, and runs on Tiger and above. The Leopard build of v6.4 is 64bit-enabled. A few support programs, used by various GRASS modules, are included in the application (gpsbabel, ppmtompeg). The TclTk GUI requires X11 - this is an optional install for OSX and can be found on the system install disk (retail, or that come with Macs). Also included is a GDAL-GRASS plugin (this used to be included in GDAL).

See the GUI Notes below for additional requirements.

NOTE: the Leopard version will not run properly on Tiger, but due to limitations of the automated package generation the installer will still let you install it on Tiger.

See the readme for startup options.

The wxPython GUI is also included. It is a work in progress, and there may be problems (report problems to the GRASS Dev or GUI lists, or bug tracker). Type "g.gui wxpython" in the GRASS terminal to start it. The wxpython GUI is not as well developed in 6.3, so you're probably better off sticking with the TclTk GUI in 6.3.

Though technically multiple versions of wxpython can be installed, the OSX installers (by design or installer "upgrade" behavior) strip out parts (but not all) of old versions, thus rendering them non-functional. Also (by design or over-zealousness), wxpython version requirements are exact when dealing with compiled extensions (nviz, vdigit). With this combination of installer behavior and version requirement, GRASS 6.3 and 6.4 can't both use the wxpython GUI.

GRASS 6.4

On Tiger, it requires Python 2.5. Leopard includes Python 2.5. wxPython is now included in the application and a separate install is not required.

GRASS 6.3

On Tiger, it requires Python 2.5 and wxPython 2.8.7.1 (exactly). Leopard includes these, so nothing extra is needed on Leopard. The wxpython GUI in GRASS 6.3 is an early development version, so use GRASS 6.4 if you want to try the wxpython GUI.

GRASS 6.4

The TclTk GUI needs ActiveTcl 8.5 (not 8.6) from ActiveState.

GRASS 6.3

An X11 Tcl/Tk is included with GRASS 6.3.

Included is a build template similar to the GEM system for modules. But it doesn't require the module source to be configured for GEM (I haven't seen any that are yet). It's a bit rough. See the included readme for details.

GRASS can be used with R (Tiger only). You should get the latest R binaries (at least 2.3.0), the mini install is sufficient (no C/Fortran for building packages from source). The R.app Package Installer is a handy GUI front-end to the install tools. Install the R GDAL package from the GDAL framework (instructions are included with it). Install the maptools binary package from the CRAN binary repository. Install the spgrass6 from the CRAN source repository. See the GRASS stats page for instructions on use.

For GRASS to run on Panther, download the source and see the included Mac OS X build notes for help on how to compile from source.