Apertium is a free/open source platform supporting the development of rule-based machine translation and other language processors. Apertium was launched in 2005; the involvement of industry, academia and independent developers during more than a decade has produced machine translation systems for many language pairs, with 40 stable systems available. The focus of Apertium as a free/open source software project is on less-resourced languages. Apertium is already integrated in computer-assisted tools such as OmegaT and MateCat and may be used online or offline. The free/open source philosophy in Apertium encourages the sharing of translation resources and establishes a continuum between researchers, developers, vendors and users: a community, which encourages the involvement of translators and language activists in its development. In this session we will present the platform and the resources available, discuss applications and describe success stories.