This chapter discusses the role of the project/product community in the open source product life cycle. It outlines how a community-driven approach affects not only the development process, but also (and more importantly) the marketing/sales process, the deployment, the operation, and in general the resulting software product. Participation in the community is essential for any organization using the product, leading to the concept of a community customer. Specific community participation guidelines are given to organizations and individuals who deploy and use open source software, further develop it, or offer lifetime services on the product.