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GPLv3 and Copyleft
The GNU General Public Licence v3 is the most widely known copyleft licence. It ensures that software and its derivatives remain free forever (the viral effect).
Core Concept
Strong copyleft: anyone who modifies and distributes software under GPLv3 must make the modified source code publicly available under the same licence. Version 3 also explicitly addresses patent rights and anti-tivoisation (protection against hardware locks).
Assessment
- For organisations: Caution is required. Integrating GPL code into proprietary desktop or mobile applications may create an obligation to disclose the entire product.
- For OSS authors: The safest method for permanently protecting a project's freedom against proprietary forks.