The MIT license is a short, permissive open-source license that lets you do almost anything with the software, including using it commercially and in closed-source products, as long as you keep the original copyright and license notice with it. That is the whole summary in one sentence. Everything else is nuance around one obligation and one disclaimer.
MIT is the most common license on GitHub and across the npm and PyPI ecosystems for a reason: it is easy to comply with, business-friendly, and short enough to read in under a minute. But "easy" is not "automatic," and the single condition it imposes is exactly the thing teams forget at scale.
What the MIT License Lets You Do
The grant is broad. Under the MIT license you may:
- Use the software for any purpose, commercial or private
- Copy and distribute it
- Modify it however you like
- Merge it into larger works
- Publish, sublicense, and even sell copies or derivative products
There is no requirement to release your own source code, no obligation to publish your modifications, and no royalty. You can take MIT-licensed code, change it, wrap it in a proprietary product, and sell that product without sharing anything back. This is what makes MIT "permissive" as opposed to "copyleft."
The One Condition: Preserve the Notice
MIT imposes exactly one requirement. The copyright notice and the permission notice, meaning the license text itself, must be included in all copies or substantial portions of the software. That's it.
In practice this means when you redistribute MIT-licensed code, you carry along its LICENSE file or an equivalent notice attributing the original authors. For a single dependency this is trivial. The failure mode appears at scale: a typical application depends on hundreds of MIT-licensed packages, each with its own copyright holder, and honoring the condition means aggregating all of those notices into your distribution. Most teams that "violate" the MIT license do so not out of malice but because they never generated the attribution file.
The Warranty Disclaimer
The second half of the license is a disclaimer written in capital letters: the software is provided "as is", without warranty of any kind, and the authors are not liable for any claim or damages arising from its use. This is why the license is short and why maintainers give away code freely. If an MIT-licensed library has a bug that costs you money, you have no legal recourse against its authors. You accept the risk when you adopt the dependency, which is a good reason to actually evaluate what you pull in rather than trusting a name.
MIT vs Other Common Licenses
A quick orientation among the licenses you will meet most:
- MIT and ISC are functionally equivalent permissive licenses; both require only attribution. ISC is essentially MIT with slightly trimmed wording.
- Apache License 2.0 is also permissive but longer, adding an explicit patent grant and a requirement to state significant changes. Many organizations prefer it in enterprise settings for that patent clause.
- BSD licenses (2-clause and 3-clause) are close cousins of MIT; the 3-clause adds a no-endorsement provision.
- GPL and LGPL are copyleft: derivative works must be released under the same license, which is a very different obligation.
- AGPL extends copyleft to software offered over a network, which can catch SaaS teams by surprise.
If your dependency tree is all MIT, ISC, Apache-2.0, and BSD, you are in permissive territory and your obligations are attribution-shaped. The moment a GPL or AGPL package appears, the calculus changes, and you want to know before you ship. We walk through the runtime case in our Node.js licensing guide.
Meeting the Condition in Practice
For a real project, honoring MIT across hundreds of dependencies is an automation problem, not a legal one. Generate an attribution report from your lockfile on every build so it reflects the exact set of packages you ship, and include that report in your distribution. Define a license policy that classifies MIT, ISC, Apache-2.0, and BSD as allowed, flags copyleft for review, and enforce it in CI so a disallowed license fails the build rather than surfacing during due diligence for a funding round or acquisition. Software composition analysis such as Safeguard's SCA reports each component's license alongside its known vulnerabilities, which keeps the compliance and security views in one place.
FAQ
Can I use MIT-licensed code in a commercial, closed-source product?
Yes. The MIT license explicitly permits commercial use and imposes no requirement to open your source or share modifications. Your only obligation is to include the original copyright and license notice with the MIT-licensed portions you distribute.
Do I have to publish changes I make to MIT-licensed code?
No. Unlike copyleft licenses such as the GPL, MIT does not require you to release modifications or derivative works. You can modify the code privately and keep those changes proprietary, provided you still preserve the original notice.
What exactly counts as "including the notice"?
Carry the copyright line and the license text with the software you redistribute, typically as a LICENSE file or an aggregated attribution document. For an application with many MIT dependencies, generate a combined notices file listing each package's copyright and license so every original author is credited.
Is the MIT license compatible with GPL projects?
Yes, in the direction that matters: MIT-licensed code can be incorporated into a GPL-licensed project, because MIT's permissive terms do not conflict with GPL's requirements. The combined work as a whole then falls under the GPL. The reverse is not true, since GPL's copyleft would impose obligations MIT does not.