GRASS GIS is free software,
anyone may develop his/her own extensions. The GRASS GIS
Add-ons Wiki page contains a growing list of links to GRASS GIS
extensions, which are currently not part of the standard
They can be easily installed in the local installation through the graphical user interface (Menu - Settings - Addons Extension - Install) or via the g.extension command.
These manual pages are updated daily.
How to contribute?
You may upload your add-on to the GRASS Add-ons repository. Further details about gaining write access to our Git repository can be found in this document. Please also read GRASS GIS programming best practice.
How to get the source code:
git clone https://github.com/OSGeo/grass-addons.git