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Topic 2 - Licensing and Legal Aspect of Open Source Software

target_audience Target Audience: Developers

objectives Objective: By the end of this topic, participants will be able to: (1) explain what an open source is, (2) distinguish between the main categories of licenses, (3) understand developers’ rights and obligations under different license types and (4) choose the correct licence for their code.

I. Introduction

The open source movement has started from the tech world and thus it implied technical people with a clear ethical direction, yet not very fond of working with laws and regulations, but open source at this very heart has an important legislative facet too.

Open source is not just publishing code online; it’s about establishing a licence that describes what can be done with it and even more, a way that the entire ecosystem around the released code (other coders, users) is organised (Ilie, 2024). Basically, it is an official document that contains the terms and conditions about how to use, modify and share the code. Ignoring those rules can lead to various legal conflicts such as lawsuits, forced compliance or financial penalties.

The Open Source Initiative (OSI) is the non-profit organization which is significantly contributing to defining and disseminating relevant aspects of what open source licensing is and what it is not. As we showed in the Topic 1 - Inside the World of Geospatial Open Source and Its Educational Initiative, this organization is the steward of the Open Source Definition and plays a crucial role in drafting a robust foundation for the open source software ecosystem. For the definition of Open Source concept ten criteria must be complied. And all of them are related to the distribution terms, that is, the license.

II. Types of Open Source Licenses

There are hundreds of different open source software licenses in use, but, mainly, two categories of open source licence can be separated: copyleft and permissive.

  • Copyleft licenses. The term ”copyleft” was used and defined into a legal concept by the programmer Richard Stallman, founder of the GNU General Public License Project, and is the opposite of the term "copyright", indicating that redistribution is permitted. It is even graphically represented by an inverted copyright symbol. In other words, you can use, modify and share the code, but if you redistribute it you must keep it open source under the same terms. There are two main copyleft licenses:

    • strong copyleft license - refers that any derivative works must be licensed under the same terms as the original. For example, if you redistributed a program that includes GPL code written by someone else, you must make your program available under GPL licenses, too.

    • weak copyleft licenses - it offers more flexibility, in the sense that allows developers to combine the original work with additional or modified code. The newly added files can be released under the same license or under a different license.

  • Permissive licenses are among the most popular open source licenses because, as the name suggested, they have fewer restrictions on usage and redistribution. More exactly, you can modify, copy or complete the code without the obligation to share the updates. In general, the only common requirement is the attribution of the original code to the original developers. In this context, the advantage, which makes them popular, is that they allow integration into proprietary software.

Of the two categories of open source licenses, the most popular are permissive licences (for example, MIT and Apache 2.0), followed by the copyleft licenses such as GPLv3 (Open Source Guides).

III. Legal Aspect

Computer software is the result of the intellectual work of one or more people, therefore it is default protected by copyright legislation. This means that no one can use, copy, or modify that code without the original author's permission. For example, the US copyright law gives copyright owners six exclusive rights (Chintalapoodi, 2023):

  • The right to reproduce and make copies of an original work;

  • The right to prepare derivative works based on the original work;

  • The right to distribute copies to the public by sale or another form of transfer, such as rental or lending;

  • The right to publicly perform the work;

  • The right to publicly display the work, and

  • The right to perform sound recordings publicly through digital audio transmission.

In the European Union, copyright protection grants the following exclusive rights (European Union, n.d.):

  • economic rights – guaranteeing control over the work and remuneration for its use through selling or licensing,

  • moral rights – usually protecting the rights to claim authorship (right of attribution) and to refuse a modification of the work (right of integrity).

By applying an open source license, you are granting a set of permission to others, while still retaining the underlying copyright. As a developer, when choosing a license for your open source project, it would be a good idea to answer a few essential questions (Karagozgil, 2023):

  • How do I want someone else to use my code?

  • How permissive do I want to be?

  • Do I want to allow it to be used in commercial products?

  • Do I want to require that any changes to my code be released under the same license?

  • What kind of community do I want to attract?

IV. Don’t know what license is appropriate for your project? The application https://choosealicense.com/ can be a useful tool in determining the right open source licences for your project. Using this application, the folowing table of the most popular open source licenses was created (Table 1).It should be read following the quidelines:

  • Open source licenses grant to users 🟢permissions to do things with licensed works copyright or other "intellectual property" laws might otherwise disallow. Most open source licenses' grants of permissions are subject to compliance with 🔵conditions. Most open source licenses also have 🔴limitations that usually disclaim warranty and liability and sometimes expressly exclude patent or trademark from licenses' grants.
  • Commercial Use: 🟢This software and derivatives may be used for commercial purposes. Distribution: 🟢You may distribute this software. Modification: 🟢This software may be modified. Patent Use: 🟢This license provides an express grant of patent rights from the contributor to the recipient. 🔴This license explicitly states that it does NOT grant you any rights in the patents of contributors.
  • Private Use: 🟢You may use and modify the software without distributing it.
  • Disclose Source: 🔵Source code must be made available when distributing the software.
  • License and Copyright Notice: 🔵Include a copy of the license and copyright notice with the code.
  • Network Use is Distribution:🔵Users who interact with the software via network are given the right to receive a copy of the corresponding source code.
  • Same License: 🔵Modifications must be released under the same license when distributing the software. In some cases a similar or related license may be used.
  • State Changes: 🔵Indicate changes made to the code.
  • Hold Liable: 🔴Software is provided without warranty and the software author/license owner cannot be held liable for damages.
  • Trademark Use: 🔴This license explicitly states that it does NOT grant you trademark rights, even though licenses without such a statement probably do not grant you any implicit trademark rights.

Table 1 - The most popular open source licenses, detailing the permissions and restrictions of each, allowing an easy comparison (Ilie, 2025)

LicenseCommercial UseDistributionModificationPatent UsePrivate UseDisclose SourceLicense and Copyright NoticeNetwork Use is DitributionSame LicenseState ChangesHold LiableTrademark Use
Academic Free License v3.0🟢🟢🟢🟢🟢🔵🔵🔴🔴
GNU Affero General Public License v3.0🟢🟢🟢🟢🟢🔵🔵🔵🔵🔵🔴
Apache License 2.0🟢🟢🟢🟢🟢🔵🔵🔴🔴
BSD 2-clause "Simplified" License🟢🟢🟢🟢🔵🔴
BSD 3-clause Clear License🟢🟢🟢🔴🟢🔵🔴
BSD 3-clause "New" or "Revised" License🟢🟢🟢🟢🔵🔴
Eclipse Public License 1.0🟢🟢🟢🟢🟢🔵🔵🔵🔴
European Union Public License 1.1🟢🟢🟢🟢🟢🔵🔵🔵🔵🔵🔴🔴
GNU General Public License v2.0🟢🟢🟢🟢🔵🔵🔵🔵🔴
GNU General Public License v3.0🟢🟢🟢🟢🟢🔵🔵🔵🔵🔴
ISC License🟢🟢🟢🟢🔵🔵🔵🔵🔴
GNU Lesser General Public License v2.1🟢🟢🟢🟢🔵🔴
GNU Lesser General Public License v3.0🟢🟢🟢🟢🟢🔵🔵🔵🔵🔴
MIT License🟢🟢🟢🟢🔵🔴
Mozilla Public License 2.0🟢🟢🟢🟢🟢🔵🔵🔵🔴🔴
Microsoft Public License🟢🟢🟢🟢🟢🔵🔴🔴
Microsoft Reciprocal License🟢🟢🟢🟢🟢🔵🔵🔵🔴🔴
Open Software License 3.0🟢🟢🟢🟢🟢🔵🔵🔵🔵🔵🔴🔴
The Unlicense Do What The F*ck You Want To Public License🟢🟢🟢🟢

After reviewing the main software licenses, it is important to note that GitHub is one of the most popular platforms, chosen by many developers for hosting code for open source projects. According to the statistics at the beginning of 2025, over 100 million developers use GitHub (Burnett & Kinder, 2025). When you publish/create a new project on GitHub, you have the option to make the repository private or public. Attention! This is not the same as licensing your project. If you want others to use, modify, share or contribute to your project, you must include an open source license (Open Source Guides).

V. Discussion questions

  1. Which is the organization that maintains the Open Source definitions?

  2. What are the two main types of open source licensing? What is the difference between them?

  3. Discuss the importance of the licenses in the open source software industry.

  4. Reflect on the legal risk of using open source software in commercial projects without checking the license.

References