The OpenD6 Project

From the introduction: The OpenD6 Project exists to provide a unified system reference document for the OpenD6 rules and to promote the use of OpenD6 in new products by making the rules accessible and adaptable. ... This System Reference Document intends to enable continued development of OpenD6 as a comprehensive customizable game system that will remain freely accessible and to provide a platform for new creators to enter the hobby and build upon a common and completely interactive set of rules that is better viewed as a “living document” than as a definitive, finalized, and inflexible codex.