The open source and free software communities are also critical to the practical enforcement of open source and free software licenses. While the discussion so far has focused on the legal and practical reasons why open source and free software licenses tend to be complied with, there is a more fundamental reason why most programmers comply with such licenses. Non-compliance, or at least knowing non-compliance with the terms of these licenses, is simply wrong.
The world of open source and free software licensing is still a relatively small one. As has already been described in previous chapters, the code written under these licenses is mostly the work of volunteers who have dedicated huge amounts of time, and, in many cases, significant parts of their lives to the development and distribution of good code for the benefit of as many people as possible. In the course of writing this code and supporting these projects, these programmers have foregone significantly more lucrative opportunities offered by commercial software companies. Behind the black and white terms and restrictions of these licenses, which have taken up the bulk of this book, is a real principle. Free code, however free may be defined, is a social good in itself. This is the goal that is being pursued. However that goal may be reached, whatever avenue of development is followed, this principle is held above all others.
This principle is deeply felt by this community. The gross violation of it by taking someone else's work and distributing it as one's own is unthinkable. This moral principle is, by itself, responsible for the largest part for the enforcement of open source and free software licenses, not the texts of the licenses themselves, and not the courts that enforce those licenses.
 For more discussion of this principle, see the essay Homesteading the Noosphere in The Cathedral & The Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary, Eric S. Raymond (O'Reilly 2001) (rev. ed.), and the chapter The Art of Code in rebel code: inside linux and the open source revolution, Glyn Moody (Perseus Publishing 2001).
Even those who have not internalized this principle have good reason to abide by the norms of this community. Violating those norms will incur, at the least, the displeasure of this community. Given the number of people in this community and, perhaps more importantly, the knowledge and capabilities of its members, such a violation can result in the ostracism of the violator. Such a person might find his emails remaining unanswered, being ignored or flamed in usegroups, and being excluded from projects, whether under the open source or free software banner, that involve members of this community.
 Those interested in the enforcement of social norms that parallel legal restrictions should read Order Without Law: How Neighbors Settle Disputes, Robert C. Ellickson (Harvard, 1991). While this book addresses primarily the enforcement of social norms among cattle ranchers in Shasta County, California, its analysis is no less applicable to "virtual" communities such as the open source and free software communities.
This does not mean there is a univerally shared view as to the purpose of open source and free software licensing or the best way to realize that purpose. As noted earlier, there are real ideological differences between, for example, the "open source" community and the "free software" community. That said, there is considerable common ground. One principle, which is universally accepted, is that taking someone else's work and modifying or distributing it in disregard of the intent of its creator is wrong.
This should not be confused with the "cross-over" of programmers (and their code) from an open source project to a proprietarily licensed projects. As described at the end of Chapter 2, prominent open source programmers such as Bill Joy and Eric Allman moved from open source to proprietary projects. In Allman's case, he maintained both open source and proprietary distributions of his popular Sendmail program in a way consistent with both the terms and the principles of the original license. Such movement does not (and should not) result in any ill feeling against such individuals.
In sum, while contracts and courts are fundamental to protecting the principles of open source and free software licensing, the real guardians of these principles are programmers (and users) themselves.