open-source license

basicwidespread

A legal permission that allows anyone to freely use, examine, modify, and redistribute a software or AI model under specified conditions.

In plain terms

Imagine a chef not only handing over the finished dish but also the recipe, along with a note: 'Cook it, adapt it, share it, even for money.' An open-source license is this note: a legal text specifying what you may do with someone else's work.

Without a license, copyright essentially prohibits almost everything by default: even if you see the code on the internet, you cannot use it freely. The license grants permission, which is why much of the world's software can be built on collaboratively developed, freely available building blocks.

Licenses are not uniform. Permissive ones (such as MIT, Apache 2.0) mainly require you to preserve the copyright notice and the license text. 'Copyleft' types (such as GPL) also mandate that if you distribute a modified version, its source code must be made available under the same license.

The situation with AI is more complex because a model consists not only of code: there are also the trained weights and training data. Many models called "open" can be downloaded, but the license restricts, for example, commercial use, meaning they are not open source in the strict sense.

How it works

The rights holder (the author or, for example, the employer company) owns the work based on copyright and decides whether to share it: they select a well-known license and attach its text to the code or the model.
The license lists what is permitted: use, study, modify, and distribute. It also specifies the conditions, such as attributing the author's name or making the source code available upon distribution.
Anyone exercising rights granted by the license, such as modifying or redistributing the work, must comply with the terms. No separate contract or permission request is required.
If someone violates the terms, for example by distributing a modified version of copyleft code without the source code, they may lose their right to use it, and the rights holder can take legal action.
The Open Source Initiative (OSI) examines which licenses meet the definition of open source, and since 2024 it has a separate definition for open-source AI.

An everyday example

A small business wants its own customer service agent, so it downloads a free language model from the internet. Before using it in production, it checks the license: if it is Apache 2.0, it can be integrated into a paid service provided the conditions (such as retaining the license text and copyright notices) are met, but if the license permits only research purposes, it is not suitable for commercial use.

Who is affected

developerYou must know the license of every code library and model used, as these determine what you can do with your own product. → Code

entrepreneur, executiveA poorly chosen license for a model or software can pose legal risks and incur retroactive conversion costs for the company.

lawyer, citizenThe license influences how far outsiders can see into the systems that affect our daily lives, and how far they can scrutinize them. → Law

parent, student, teacherOpen-licensed tools can be used for free for learning, and you can look into how they work. → Education & Family

A common misconception

MythIf something is open-source, I can do whatever I want with it since it is free.

In realityOpen-source licenses also set legally binding conditions, such as attributing the author or sharing the source code upon redistribution. Free of charge is not the same as open: the license of many free-to-download AI models is explicitly restrictive.

Limits and risks

AI companies use the term 'open' for marketing purposes, so always check the actual license text, not the press release.
A license concerns the right to use and provides no guarantee: open-source software typically arrives on an "as is" basis, and the license excludes the author's liability to the greatest extent possible. If someone incorporates them into a product, that person is responsible for the product.
Mixing elements with different licenses can lead to conflicts, because a copyleft component can affect the distribution terms of your entire product.
An open license alone does not settle whether the model's training data was collected lawfully, nor does it address liability for the model's output.

Similar, but not the same

open-weight model – Here, only the trained model weights can be downloaded, but the training code, data, and right to free use are not necessarily included.
ingyenes szoftver (freeware) – Freeware costs nothing, but its source code is generally not available, and you cannot freely modify or redistribute it.
Creative Commons licenc – It operates on a similar principle but is primarily designed for text, images, music, and data; Creative Commons itself does not recommend it for software.

Related concepts

Broader

Narrower

permissive license, copyleft, GPL, MIT-licenc, Apache-licenc

On the edge

open-source model, open-weight model, open-source AI, closed model, EU AI-rendelet

A brief history

One of the first and still defining licenses of this kind, the GNU General Public License (GPL), was published in 1989 as the work of Richard Stallman. The term "open source" and the Open Source Initiative that maintains it were born in 1998, and the organization published the first definition of open-source AI in 2024.

Where things stand

It has been a fundamental, established tool in the software world for decades. With AI models, however, debate continues as of late 2026 over what truly counts as open. The EU AI Regulation grants exemptions from certain obligations for AI systems and models released under free and open-source licenses. This exemption does not apply to models posing systemic risk, nor to prohibited or high-risk applications. Compliance with copyright rules and the provision of a summary of training data remain mandatory for open models.

Status: 2026 November

In the news

Appears in 1 Agent Age stories; the curve shows weekly occurrence in the news magazine.

South Korea allows copyright registration of AI-assisted music, while US courts often deny protectionAug 4, 2026 · Jog

Also known as

open-source license · open-source license · open-source licenc · open source license · open-source licence · szabad szoftveres licenc · FOSS-licenc · OSS-licenc

Sources

This entry was machine-edited and has undergone machine expert review; the “In the news” section updates automatically from Agent Age stories.