farmOS is a web-based application for farm management and planning. It is built on Drupal, which makes it modular, extensible, and secure. Openlayers is used for mapping and geodata manipulation.
AgroSense is a free and open source farm management and decision making software. The source code is available at bitbucket & check the limetri website. You can also download the Windows & Linux executables of this software from website atdownloads page
Open Ag Toolkit ( OpenATK ) makes it easier to manage farms by improving the way farmers are able to collect and use information. written some simple, free, open-source mobile apps that sync across everyone on a farm through existing cloud services like Trello and Dropbox. You can find the source codes for these apps at github , also you can visit OpenATK website.