Boxer is designed to support and encourage open development of resources and tools. We want to empower educators at any level of technical expertise to modify, extend, or build from scratch. To this end, we very much want to see wide-spread grassroots creation of "materials the live and grow" as they are improved, extended and adapted to local circumstances. As a matter of principle, all materials developed at UC Berkeley are completely open and free of copyright restrictions. We encourage other developers not only to follow this principle, but also to anticipate re-use and extension by making materials (1) that are simple to understand and modify, (2) that are well-documented, and (3) that are openly available.