We introduce a new principle, the Open Authorial Principle, that characterises desirable properties of languages supporting networks of authors. We survey the growth in generosity of authorial systems, in a progression starting with traditional object-orientation, continuing through aspect-oriented, subject-oriented, context-oriented and dependency injection systems, and concluding with the most recent generation of highly dynamic systems such as Korz and Newspeak. We follow the implications of our principle for the externalisation of application designs, resulting from the need to promote the representation of differences between programs as valid programs themselves. This raises conceptual and practical parallels with technologies and idioms supporting the web, such as REST, realised document structures supported by the DOM, and the negotiated space of CSS selectors. These parallels lead to a quite different organisation for the language and runtime of an openly authorable system, which emphasises a publicly addressable cellular structure and a largely static dispatch.