The NTP License is MIT-style permissive with one extra rule: keep the notice, and do not use the copyright holder's name in advertising.
On this page
What it does
The NTP License is a short permissive license from the NTP project and the University of Delaware. Permissive means you can put the code inside a closed product, charge for it, and keep your own source private. The condition attached is a notice condition: the copyright line and the permission notice have to stay in every copy and in the supporting documentation. It adds one rule MIT does not have. You may not use the copyright holder's name in advertising or publicity about the software without written permission.
Details
For most products this license changes nothing about how you build or deploy. You can host it as a service, ship it inside a mobile app, or link it into a closed binary without publishing anything of your own. Two things still need attention. The notice has to travel with the copies you distribute, and your marketing cannot use the copyright holder's name as an endorsement. NTP code usually sits deep inside a time-sync or networking utility, so the team that ships the binary often does not know it is there.
Pros
- Easy to drop into a closed, paid product. Procurement has seen this family hundreds of times.
- No copyleft on your own files. You keep your source private.
Cons
- The notice duty is easy to miss in a desktop, mobile, or container build. A web page is not a substitute for notices inside the artifact.
- Buyers who want an express patent grant will ask you to prefer Apache-2.0 over a short MIT-style text.
What it allows and requires
Choose a category to see the full grant in one scannable list. Permissions show what the license allows, limits show what it withholds, and obligations show the conditions your release process must satisfy.
Permissions
Commercial use
You may ship the code inside a paid product. The license does not restrict commercial use.
Modify
You may change the code, including keeping those changes private, unless a later obligation says otherwise.
Distribute
You may give copies to others. Distribution is what usually turns notice and source duties into real work.
Sublicense
You may include the code under your own product terms, so long as you still meet this license's conditions.
Private use
Use inside your company, including internal forks, does not by itself trigger distribution duties.
Limits
Hold liable
The authors disclaim warranty. Recipients cannot hold them liable for damages arising from the software, except where law forbids that disclaimer.
Use trademark
The license is not a trademark license. Names, logos and product marks stay with their owners unless a separate grant says otherwise.
Patent grant
The text does not grant patents. If buyers want an express patent grant, Apache-2.0 is the usual alternative.
Obligations
Include copyright
Keep the copyright line with every copy or substantial portion you distribute.
Include license
Keep the license text with every copy or substantial portion you distribute. A web page is not a substitute for notices inside a shipped artifact.
What NTP requires when you ship
When a copy that includes NTP code leaves your company, the grant is broad and the paperwork is easy to miss. Distribution here means an installer, a mobile binary, a container image, or an SDK another team embeds. Work this list against the artifact you actually hand over, not against a README. A hosted service that never gives out a copy still belongs on the record, but the notice duty does not fire until a copy exists.
You are meeting the notice condition when the copyright line and the permission notice ship with every copy you distribute, including the documentation that accompanies a binary.
You are meeting the advertising rule when no marketing page, press release, or app store listing uses the copyright holder's name as an endorsement of your product.
You have nothing further to do for a hosted service or an internal tool, because the license attaches its condition to copies you hand to other people.
Your duties are the same whether you modified the code or not. NTP asks for no change log, no source offer, and has no rules about linking.
The duties named in NTP
The license text itself is short. These are the named conditions. They follow the code, including files you vendor into your own repository and transitive packages in the lockfile.
Include copyright
Keep the copyright line with every copy or substantial portion you distribute.
Include license
Keep the license text with every copy or substantial portion you distribute. A web page is not a substitute for notices inside a shipped artifact.
Things to be aware of
- Teams treat NTP as MIT and forget the advertising rule. Read the name clause once, then keep the copyright holder out of your marketing copy.
- A single vendored file loses its header comment, which is exactly where the notice lives. Copy the notice with the code, or keep the LICENSE file beside it.
- The notice ends up only on the public attestation page and never inside the shipped artifact. A desktop or mobile build needs its own bundled licenses screen.
What the NTP License does not do
Search results often flatten NTP License into a slogan. These are the usual misreads. NTP is a grant with conditions, not a permission to skip the paperwork below.
- the NTP License does not require you to publish your own source. Combining it with closed code is the point of the grant.
- the NTP License does not mean "no obligations." The copyright line and license text still have to travel with copies you hand to other people.
- It is not a patent license unless the text says so. MIT-family grants say nothing about patents.
How NTP differs from nearby licenses
These licenses are often confused with NTP, but their release duties differ. Each row summarizes what the license requires when you ship. Open the linked page for the full checklist.
- NTP
- The NTP License is MIT-style permissive with one extra rule: keep the notice, and do not use the copyright holder's name in advertising.
- MIT
- MIT lets you ship the code inside a closed, paid product. The one condition is that the copyright line and license text travel with every copy.
- BSD-3-Clause
- Permissive like MIT, with one extra rule: you may not use the authors' names to promote your product. Notices travel with source and binaries.
- Apache-2.0
- Permissive like MIT, plus an express patent grant. The catch is the NOTICE file: it has to travel inside the binaries you ship.
Common questions about NTP License
Answers to common questions about what NTP License requires, when its duties apply, and what evidence belongs with a release.
What is the NTP License?
The NTP License is a short permissive license from the NTP project and the University of Delaware. Permissive means you can put the code inside a closed product, charge for it, and keep your own source private. The condition attached is a notice condition: the copyright line and the permission notice have to stay in every copy and in the supporting documentation. It adds one rule MIT does not have. You may not use the copyright holder's name in advertising or publicity about the software without written permission.
What does NTP require when you ship a product?
You are meeting the notice condition when the copyright line and the permission notice ship with every copy you distribute, including the documentation that accompanies a binary. You are meeting the advertising rule when no marketing page, press release, or app store listing uses the copyright holder's name as an endorsement of your product. You have nothing further to do for a hosted service or an internal tool, because the license attaches its condition to copies you hand to other people. Your duties are the same whether you modified the code or not. NTP asks for no change log, no source offer, and has no rules about linking.
Does NTP require me to open my own source?
It is not a patent license unless the text says so. MIT-family grants say nothing about patents.
How do I attribute NTP in a product I ship?
Attribution for NTP means the copyright line and the license text travel with every copy a recipient actually gets. That can be an about screen, a licenses file inside the installer, or a notice in the container image. A public page helps a buyer audit the inventory. It does not replace notices inside the artifact. If you copied files into your own repository, the header on those files still has to stay.
Is a website notice enough for NTP?
No. NTP talks about copies. A public attestation page is the honest list for procurement. The condition is met when the notices sit in the material you hand over. Put them in the installer, the about screen, or a licenses file inside the binary, then keep the same texts on the page.
Do transitive NTP dependencies count?
Yes. The condition follows the code, not the package you chose by name. If the lockfile pulled in NTP transitively and you distribute that tree, those notices travel too. Listing only direct dependencies is how teams miss the duty.
How is NTP different from MIT License?
NTP asks this: The NTP License is MIT-style permissive with one extra rule: keep the notice, and do not use the copyright holder's name in advertising. MIT License asks this: MIT lets you ship the code inside a closed, paid product. The one condition is that the copyright line and license text travel with every copy. Open the MIT License page for what that license requires when you ship. Do not treat the SPDX ids as interchangeable because the short names look similar.
Where do I record NTP for a buyer?
SourceTrust fetches the published artifact for the package, extracts the license files it contains, and compares that text against the SPDX id the package declares. Only a confirmed match fills in the license text for you. Every other outcome waits for a person to accept it. The stored text is what your published attestation page and every export file carry, so the notice you ship can be built from the same record.
Where do I record NTP for a buyer?
SourceTrust fetches the published artifact for the package, extracts the license files it contains, and compares that text against the SPDX id the package declares. Only a confirmed match fills in the license text for you.
Every other outcome waits for a person to accept it. The stored text is what your published attestation page and every export file carry, so the notice you ship can be built from the same record.
Read /docs/auto-fetch-license for how the fetch decides.
See also
The hub is the pillar for this cluster. Sibling licenses are the other spokes. Product FAQ links explain how SourceTrust records the duty, not the license text itself.
Practical guidance for procurement review, not legal advice. Confirm high-stakes use with counsel.