"Freedom or Power?" (~2001), coauthored by stallman and bradley-kuhn, addresses a rhetorical move sometimes made by critics of copyleft: the claim that requiring derivative works to be free is itself a restriction of freedom, and that truly free software would use permissive licenses that impose no conditions on redistribution. stallman and bradley-kuhn argue that this conflates two very different kinds of freedom — the freedom of developers to do whatever they want with software, and the freedom of users to use, study, modify, and redistribute software they receive.
The essay's central distinction is between freedom and power. The ability to take free software, modify it, and distribute the modified version under a proprietary license is not a freedom in the relevant sense — it is power over other people, specifically the power to restrict their freedom. Permissive licenses grant developers this power; copyleft licenses do not. The question is whether this power — the power to make software nonfree — is the kind of thing the free software movement should protect.
stallman and bradley-kuhn argue that it is not. The free-software-foundation's goal is user freedom — the four-freedoms — not developer power. copyleft, as implemented in gpl-v2 and gpl-v3, restricts developer power specifically in order to protect user freedom. This is not a contradiction of free software principles but their application.
The essay responds to arguments heard frequently in the context of the open-source-definition-schism and the preference of many open source advocates for permissive licenses like BSD or MIT. Those advocates sometimes framed their preference as more "liberal" or more "free" than copyleft. stallman and bradley-kuhn reject this framing: the question is not which license imposes fewer restrictions on developers, but which licensing regime best promotes the freedom of all users of software.
bradley-kuhn's coauthorship reflects his role as a key figure in the software-freedom-conservancy and his longtime collaboration with stallman on questions of GPL enforcement and interpretation.