Read access is granted to the public, write access
must be requested, see here for details:
https://trac.osgeo.org/grass/wiki/HowToContribute#WriteaccesstotheGRASSaddonsrepository
However, it is also possible to fork this repository, insert your AddOn or fix an existing one in a new branch and finally open a pull request.
In either case, please read the submitting rules at the bottom of this page.
Clone of the entire AddOns git repository:
git clone https://github.com/OSGeo/grass-addons.git grass_addons
The simplest way to install GRASS GIS AddOns is to use the g.extension
module:
https://grass.osgeo.org/grass76/manuals/g.extension.html
Preparations (assuming source code in $HOME/grass76/): (if you have already build GRASS from source you don't need to do this again. If adding to a binary install the versions must match exactly. For a git clone this means that the main GRASS binary and source code versions (GRASS GIS 6 or 7) must match.)
./configure # [opionally flags]
make libs
The easiest way to compile GRASS AddOns modules into your GRASS code is by setting MODULE_TOPDIR on the fly to tell 'make' where to find the prepared GRASS source code:
make MODULE_TOPDIR=$HOME/grass76/
(adapt to your /path/to/grass76/). Each module/script in the GRASS AddOns git repository should have a Makefile to support easy installation.
Install then into your existing GRASS installation with
make MODULE_TOPDIR=$HOME/grass76/ install
For system-wide installation this usually requires "root" priviledges (so, also 'sudo' may help).
compile GRASS AddOns modules into your GRASS code by setting MODULE_TOPDIR to where to the GRASS binaries are located:
make MODULE_TOPDIR=/usr/lib/grass76/
To submit your GRASS GIS module here, please check
https://grass.osgeo.org/development/
The submmission must be compliant with the GRASS submission rules as found in the GRASS source code and RFC2 (Legal aspects of submission):
https://trac.osgeo.org/grass/wiki/RFC
Also read submitting instructions before committing any changes!