COPYLEFT OPEN-SOURCE SOFTWARE LICENSES

 

Copyleft or protective licenses are very popular among open-source software. By definition, they prohibit the usage of this software as a part of the proprietary software product with a copyright belonging to the third-party. A relicensing or dual-licensing approach is not allowed either. The copyleft licenses enforce keeping the software source code open for the community even though some confidential or commercial-project specific changes are required to be introduced in it. The permissive licenses, on the other hand, allow the software to be relicensed towards a more or less protective direction or even to become a part of the closed copyright product.

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The GNU General Public License (GPL) is the most popular example of copyleft licenses.