The MIT licence is a short, permissive open source licence that lets you use, copy, modify, and redistribute the code for almost any purpose, including commercial products, as long as you keep the original copyright and licence notice. That single condition is the whole deal, which is why the MIT licence sits at the top of npm, PyPI, and Maven dependency trees more than any other licence.
Because it is so permissive, developers rarely think twice before pulling in an MIT-licensed package. That convenience is exactly why the licence deserves a closer look from a security angle: permissive terms mean you inherit code with essentially no warranty and no obligation on the author to fix anything.
What the MIT licence actually says
The full text of the licence mit variant fits on a single screen. It grants "any person obtaining a copy" the right to deal in the software "without restriction," including the rights to use, copy, modify, merge, publish, distribute, sublicense, and sell copies. The only requirement is that the copyright notice and permission notice appear in "all copies or substantial portions of the Software."
The second half of the text is the disclaimer. It states the software is provided "as is," without warranty of any kind, and that the authors are not liable for any claim or damages. In plain terms: if an MIT-licensed dependency ships a vulnerability that takes down your production system, you have no legal recourse against the maintainer.
MIT licence commercial use
The most common question teams ask is whether they can build a paid product on top of MIT code. The answer is yes. MIT licence commercial use is explicitly permitted. You can bundle an MIT-licensed library into a closed-source SaaS product, ship it inside a mobile app, or sell it as part of a hardware appliance without publishing your own source.
There is no copyleft clause, so unlike the GPL, the MIT licence does not force your derivative work to adopt the same licence. You are not required to open source your changes. The one thing you must do is preserve attribution. Stripping the copyright notice out of a vendored file is the single most common way companies quietly violate the terms.
Why permissive does not mean risk-free
Permissive licensing removes legal friction, but it does nothing about code quality or maintenance. When you depend on an MIT-licensed package you are trusting an author who has explicitly disclaimed all responsibility. Several practical risks follow from that:
- Abandonment. MIT packages are frequently one-person hobby projects. If the maintainer walks away, unpatched CVEs can sit open for years.
- Transitive sprawl. A single direct dependency can drag in dozens of MIT-licensed transitive packages you never chose and never review.
- Typosquatting and takeover. Because MIT code is trivially forkable and republishable, malicious actors clone popular packages, add a payload, and publish under a near-identical name.
None of these are licence defects. They are consequences of a low-friction ecosystem where pulling in code costs nothing. An SCA tool helps here by resolving the full transitive graph and flagging known vulnerabilities regardless of how deep the MIT-licensed dependency sits.
Attribution obligations in practice
The preservation requirement is easy to satisfy and easy to overlook. Package managers handle it automatically when you install normally: the licence file travels with the package inside node_modules or the site-packages directory. The problem shows up when engineers copy a helper function directly into their own repo, or when a build step tree-shakes away the licence header.
For distributed binaries and container images, the accepted practice is to generate a THIRD-PARTY-NOTICES or NOTICE file that aggregates the licence text of every bundled dependency. Tools that produce a software bill of materials (SBOM) can emit this automatically, and it doubles as evidence for compliance reviews.
Comparing MIT to other common licences
It helps to see where MIT sits relative to its neighbors:
Permissive (do almost anything, keep the notice)
MIT - shortest, no patent grant
BSD-2 / BSD-3 - similar, BSD-3 adds a no-endorsement clause
Apache-2.0 - permissive + explicit patent grant + NOTICE handling
Weak copyleft (share changes to the library)
MPL-2.0, LGPL
Strong copyleft (derivative must stay open)
GPL-2.0, GPL-3.0, AGPL-3.0
One nuance worth knowing: the MIT licence contains no explicit patent grant. Apache-2.0 does. For most application code this rarely matters, but in patent-sensitive domains legal teams sometimes prefer Apache-2.0 for exactly that reason.
Building a licence policy that scales
Manually reading the licence of every dependency does not scale past a handful of packages. A workable policy defines an allowlist of licences your organization accepts by default (MIT, BSD, Apache-2.0 are almost always on it), a denylist for licences that conflict with your distribution model (AGPL is the usual example for closed-source SaaS), and a review queue for anything unrecognized.
Wire that policy into CI so a pull request that introduces a denied or unknown licence fails the build before it merges. The same scan that checks licences can check for known vulnerabilities, which is why licence compliance and vulnerability management tend to live in the same tooling. If you want to go deeper on dependency risk fundamentals, the Safeguard Academy walks through building a supply-chain policy from scratch.
FAQ
Can I use MIT-licensed code in a commercial closed-source product?
Yes. The MIT licence explicitly permits commercial use, including in proprietary and closed-source software. Your only obligation is to include the original copyright and licence notice in copies or substantial portions of the code.
Does the MIT licence require me to open source my changes?
No. Unlike copyleft licences such as the GPL, the MIT licence has no share-alike requirement. You can modify the code and keep your modifications private, as long as you preserve the attribution notice from the original.
Is MIT-licensed code safe to use?
The licence itself says nothing about safety. MIT code carries no warranty and no guarantee of maintenance, so treat every dependency as untrusted until scanned. Use SCA tooling to check for known vulnerabilities and to monitor whether the package is still actively maintained.
What is the difference between the MIT licence and Apache 2.0?
Both are permissive. The main practical difference is that Apache-2.0 includes an explicit patent grant and more detailed contribution and NOTICE terms, while the MIT licence is shorter and has no patent language. For most application code either is fine, but patent-sensitive projects often prefer Apache-2.0.