The open educational resource (OER) movement has been growing rapidly since 2001, stimulated by funding from benefactors such as the Hewlett Foundation and UNESCO, and providing educational content freely to institutions and learners across the World. Individuals and organisations are motivated by a variety of drivers to produce OERs, both altruistic and self-interested. There are parallels with the open source movement where authors and others combine their efforts to provide a product which they and others can use freely and adapt to their own purposes. There are many different ways in which OER initiatives are organised and an infinite range of possibilities for how the OERs themselves are constituted. If institutions are to develop sustainable OER initiatives they need to build successful change management initiatives, developing models for the production and quality assurance of OERs, licensing them through appropriate mechanisms such as the Creative Commons, and considering how the resources will be discovered and used by learners.