Copyleft

Copyleft is a general method for making a program or other work free and requiring that all modified and extended versions remain free as well. Rather than abandoning copyright, copyleft licenses use it strategically: where proprietary developers use copyright to take away users' freedom, copyleft uses the same legal mechanism to guarantee it. The result is that the code and its freedoms become legally inseparable.

Strong vs weak copyleft

Strong copyleft, embodied by the GPL, extends its obligations to any larger work built from the covered code, so the whole derivative must be released under compatible terms. Weak copyleft, used by the LGPL and the Mozilla Public License, limits the reciprocal obligation to the original files or library, allowing them to be linked into proprietary applications while still protecting the open component itself.

Why it suits sovereign hardware

For mining firmware and tooling, copyleft prevents a vendor from taking community improvements proprietary and locking users out of their own machines. Anyone who distributes a modified build must publish the corresponding source, keeping the software auditable. This is why D-Central releases its open projects under copyleft terms rather than abandoning them to the public.

Copyleft is one end of a spectrum; the opposite end is the permissive license, which lets recipients re-license or close derived works freely. Understanding the difference is essential before contributing to or forking any open mining project.