Open source seeds are part of a new initiative that a number of colleagues have developed, beginning in about 2011. While many of the new varieties and germplasm sources we develop in our program at UW-Madison will be released through standard 
channels via licenses to seed industry partners, we began releasing a very small amount of germplasm through an open source framework in 2014. The goal of this open source seed is to ensure it remains in the public domain for anyone’s use to grow, save, sell, replant, or breed. On April 17, 2014, this initiative released 37 varieties (including two open pollinated carrot varieties developed here at Wisconsin) that came from seven different breeding programs around the country. By the summer of 2015, that number had grown to over 65 varieties that were sold by more than 11 seed companies. Now the initiative has over 500 varieties of more than 50 crops that are sold by more than 50 seed companies. Details of the effort can be seen at osseeds.org. OSSI is also a not-for-profit entity that focuses on education and outreach about open source seeds.
An article in Crop Science by several people involved in the effort is posted here: Luby et al., 2015. We have also written an op-ed that is posted here. An article by Lisa Hamilton that covers many of the issues surrounding open source breeding is here.
The Open Source Seed Initiative was developed in part to address a growing concern among plant breeders, gardeners, farmers, citizens, and others interested in seeds. That concern focuses on the increasing intellectual property protections associated with seed and new plant varieties. The Open Source Seed Initiative is a way to place seed varieties in a “protected” commons, allowing free and open access to plant genetic resources but ensuring that these resources cannot be locked up through patents or licenses. In this way, it is our hope that open source seeds may be accessed and used by all who wish to keep these varieties and their derivatives free and accessible into the future.
For more information on this initiative, see the OSSI website or these articles relating to the project.