The repository is only for building and installing GridLAB-D from source. The installers for released versions are available at http://sourceforge.net/projects/gridlab-d/files/.
Download the source code, build, install and validate (you will need autotools)
host% git clone git@code.stanford.edu:/gridlabd/gridlabd source
host% cd source
host% autoreconf -isf
host% ./configure --enable-silent-rules --prefix=$HOME 'CXXFLAGS=-w' 'CFLAGS=-w'
host% make install
host% export PATH=~/bin:$PATH
host% gridlabd --validate
Windows users will need to install cygwin to enable building using autotools. See http://gridlab-d.sourceforge.net/wiki/index.php/MinGW/Eclipse_Installation for details.
You can setup Eclipse as your GridLAB-D modeling editor. See http://gridlab-d.sourceforge.net/wiki/index.php/Eclipse for details.
The primary manuals for GridLAB-D are online at Main Page for GridLAB-D (http://gridlab-d.sourceforge.net/wiki/index.php/Main_Page). Documentation of local projects can be found on this project's wiki (https://code.stanford.edu/gridlabd/gridlabd/wikis/home).