7-Zip GNU LGPL Licensing Guide

This article provides an overview of the licensing model governing 7-Zip, identifying the specific version of the GNU Lesser General Public License applied to its core components and outlining how its mixed-licensing structure affects developers and commercial users.

The Core License: GNU LGPL v2.1

The core code of the 7-Zip file archiver is licensed under the GNU Lesser General Public License (LGPL), version 2.1 (or later). This covers the central executable files, user interface, and primary archive management algorithms.

Under GNU LGPL version 2.1, developers are permitted to use 7-Zip's core components in both open-source and proprietary software projects. If you link against 7-Zip’s LGPL libraries dynamically, you do not need to release your own application’s proprietary source code. However, if you modify the 7-Zip source code directly, those modifications must remain licensed under LGPL version 2.1 and be made publicly available upon distribution.

Exceptions Within the Source Code

While LGPL v2.1 governs the main software, 7-Zip utilizes a mixed-license distribution for specific components within its codebase:

• LZMA SDK: The compression algorithms included in the LZMA SDK are released into the public domain, allowing complete freedom without copyleft restrictions.
• BSD License: Certain sub-modules and cryptographic components are licensed under the permissive BSD 3-Clause License.
• unRAR License: The unRAR extraction module is governed by a proprietary license from Alexander Roshal, which prohibits using the decompression code to reverse-engineer the proprietary RAR compression algorithm.

Commercial and Personal Use

Because the core software operates under GNU LGPL v2.1, standard end-users can deploy 7-Zip on any computer, including commercial, corporate, and government environments, free of charge and without purchasing individual software licenses.