OpenSource is the process of producing a software product with source code freely and openly available to one and all who wish to see it or modify it. The group of people who do this is called the OpenSourceCommunity. One web page advocating this process is http://www.opensource.org/

Predating the name OpenSource is the FreeSoftware movement. The two communities are very much aligned, but OpenSource avoids talking about principles of freedom in favour of appealing to business interests.