A Comparative Analysis of GNU GPL v2, GNU GPL v3, GNU LGPL, and GNU AGPL
A Comparative Analysis of GNU GPL v2, GNU GPL v3, GNU LGPL, and GNU AGPL
In short, open-source software is revolutionizing the whole world of software development by making collaboration, innovation, and accessibility available. The GNU General Public Licenses form the heart of this movement: a set of widely adopted licenses designed by the Free Software Foundation. These licenses define how open-source software can be used, modified, or distributed-safeguarding freedoms while keeping in line with standard legal standards.
This paper compares the fundamental differences among four important GNU licenses: the GNU General Public License, version 2; the GNU General Public License, version 3; the GNU Lesser General Public License; and the GNU Affero General Public License. Because of the increasing relevance of open-source software, developers, businesses, and organizations requiring or developing open-source software must understand the distinctions between these licenses.
What is the GNU General Public License (GPL)?
Before presenting the specific licenses, it is essential to introduce the philosophical side of the GNU General Public License, otherwise referred to as the GPL. In short, the GPL was a guarantee toward propagating software freedom. This license, in detail, ensures that users are allowed to run, study, share, and modify software. The GPL license is a strong copyleft license, meaning any derivative of GPL-licensed software needs to be freed under the same license.
The entire lifecycle of GNU GPL ensures that the software remains free and open-source-based. The two major versions used widely are version 2 and version 3, which bear different characteristics.
GNU General Public License version 2 (GPLv2)
Published in 1991, this license, GNU General Public License version 2, would soon turn into one of the most crucial licenses in open-source history. It laid the groundwork for the free software movement by making any work, when distributed under the GPLv2, to continue being open-source.
What are the Key Features of GPLv2?
Full Copyleft The GNU GPL provides full copyleft powers. That is, any derivative works made from the licensed code under GPL need to also be distributed under GPLv2. In short, if you have changed the GPL-licensed software and distributed it, then your modifications too must be released under GPLv2.
Source Code Requirement: If you distribute the software, you must provide the source code or offer to make it available to recipients. This way, the users can study, modify, and redistribute the software.
No Tivoization Protection: GPLv2 failed to address hardware restrictions on the software. Meaning some of those GPL-licensed devices were capable of running GPL-compatible software without allowing the users to modify or replace the software. GPLv3 was a solution to this.
No Patent Protection: GPLv2 does not explicitly specify provisions for patent licensing. It means that any programmer, or a company, happened to have patents on code contributed to GPLv2 projects. The legality of such makes its use uncertain.
When to Use GPLv2
GPLv2 would be a good option for projects seeking to ensure that their derivative works are open source. GPL version 2 is very relevant to communities dedicated to the social benefits of free software, and it is still quite widely used today. However, the lack of patent protection and hardware restrictions in GPLv2 has made it slightly less preferable among some developers who consider GPLv3 with full protection.
GNU General Public License version 3 (GPLv3)
To supersede GPLv2, the GNU General Public License version 3 (GPLv3) was published in 2007. The latter had been criticized over several points about which GPLv3 was drafted to provide protection, which includes restrictions over hardware, patent litigation, and compatibilities with other licenses for open-source.
Main Characteristics of GPLv3
Strong Copyleft: Like GPLv2, the GPLv3 includes copyleft provisions that insist that all derivative works must be licensed again under GPLv3.
An anti-Tivoization provision- the other big difference: The most important addition in GPLv3 is the anti-Tivoization provision. This should prevent manufacturers using GPL-licensed software in devices like a DVR or other consumer electronics, where they do not provide the user with the ability to modify or replace the software. In this way, the users' freedom to modify the software of their own devices is preserved.
Patent protection: GPLv3 has clear patent protection. Therefore, it will prevent contributors from suing users and developers for patent infringement on software licensed under the license of GPLv3. Risks involved in patent-related litigation will be reduced, and it provides a safer environment for developers and users.
Compatibility with Other Licenses: GPLv3 is more compatible with other licenses of open-source software than GPLv2. For example, GPL version 3 can coexist with the Apache License 2.0, which cannot go along with GPL 2.0. Hence, GPLv3 is more flexible while working on multiple-license projects.
Internationalization and Simplification of the Language: GPLv3 was written with an international audience in mind so that the legal jargon becomes easy to understand and faces the challenges arising from different legal systems abroad.
When to Use GPLv3
GPLv3 is appropriate when the project needs the maximum level of protection regarding software freedom. The anti-tivoization clause and patent protection make it ideal for developers who would like to make sure that users will have control over the software and will not face any patent-related legal complications.
GNU Lesser General Public License (LGPL)
The GNU Lesser General Public License is one of the derivatives of the GPL, but not the one to apply to library software libraries. The LGPL license is a weak copyleft as it does not stand for the strong copyleft, like the GPL, and thus allows people to combine code parts in their proprietary applications without obliging the whole project to be open-sourced.
Key features of LGPL:
Weak Copyleft: The LGPL requires any modifications made to the LGPL-licensed library itself but does not place copyleft requirements on the software that uses the library. This means developers are allowed to link against LGPL libraries from proprietary code without releasing the proprietary code as open source.
License Flexibility: The LGPL can be used in open-source and proprietary software. Developers can use the LGPL-licensed code with proprietary projects, but they must follow the terms of the LGPL for the library itself.
Availability of Source Code: When you are publishing an application that contains an LGPL-licensed library, the source code for that library is to be provided; however, the source code of the entire application needn't be published.
Patent Provisions: Just like GPLv3, LGPL v3 also maintains patent protection provisions that protect users from intellectual property claims about patents.
When to Use LGPL
The LGPL is apt for libraries and tools intended to be used in many different applications, including proprietary ones. The LGPL allows developers to promote wider acceptance of their libraries but ensures that improvements to the library itself are shared with the community.
GNU Affero General Public License (AGPL)
The GNU Affero General Public License (AGPL) is the adapted variant of GPL specially delivered for the networked software or as it is otherwise known, SaaS. The loophole in the GPL has been closed by the AGPL to provide access to users of networked applications to the source code, even though they cannot obtain a copy of the software directly.
Key Features of AGPL
Strong Copyleft: Similar to the GPL, the AGPL provides for strong copyleft provisions. Modifications or derivative works must be licensed under the AGPL.
Network use provision: This is the biggest difference between the AGPL and the GPL. Network use provision in the AGPL just states if you modify AGPL-licensed software that you distribute as a service over a network, you have to give access to the source code to its users. That makes them not good for large companies that could take open source as SaaS while they don't have to let their users share their change.
Patent Protection: Like GPLv3, the AGPL has patent protection to protect its users and developers against patent cases.
Availability of the Source Code: Like GPL and LGPL, if you are distributing AGPL-licensed software or even making it available as a service you will have to provide source code availability to its users.
When to Use AGPL
The AGPL is most appropriate for developers of networked applications or web services who intend to ensure that source code is always available, such as even through a web interface. It is particularly useful in the development of web servers, databases, and SaaS projects; where the usage provision also guarantees that all users benefit from the change in the software.
Conclusion
The best step toward making sure your software is used in a way that goes with your goals and values is choosing the right license for your project. Understanding the key differences between GNU GPLv2, GPLv3, LGPL, and AGPL can help guide you toward the right choice.
GPLv2 and GPLv3 will be perfectly suited for projects whose primary focus will always be on ensuring the derivative works remain open-source.
LGPL may be used when the aim is to provide some sort of flexibility to libraries while allowing the desired integration with proprietary software.
AGPL is software specifically intended for networking, where it ensures users of web services access to the source.
Choosing the appropriate type of license should allow contributions toward open-source communities without the feeling of imbalance regarding software freedom and practical usage.
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