OSET-PL-2.1 is a copyleft grant for election-system software, based on MPL with extra public-purpose terms. Read the exhibit. Not MIT.
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What it does
The OSET Public License 2.1 was written for open source election technology. It starts from Mozilla-style copyleft and adds terms aimed at public-sector use. Covered files you change and distribute have source duties. Do not assume MPL-2.0 is a substitute. Store the actual OSET text on the component.
Pros
- The grant is public and the reciprocity is written down. Buyers know what they are looking at.
- Internal use without distribution stays ordinary. The hard work starts when a copy leaves the company.
Cons
- The source-offer duty is real the moment you distribute binaries that include covered files.
- How far copyleft reaches in a mixed stack is a counsel question. Do not guess from a blog post.
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.
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.
Open your product
Copyleft can reach a combined work you distribute, not only the original files. How far that reaches in your stack is a counsel question.
Network copyleft
Classic GPL has no network clause. Offering the program as a hosted service, without distributing a copy, does not by itself trigger the source offer.
Obligations
Include copyright
Keep copyright notices on distributed copies.
Include license
Give recipients a copy of the license with the program.
Disclose source
When you distribute a binary of a covered work, corresponding source has to be offered in the way the license describes.
Same license
The combined work you distribute has to stay under this license. You cannot close the covered work with a more restrictive grant.
What OSET-PL-2.1 requires when you ship
When you distribute a binary that includes OSET-PL-2.1 code, notice still travels with the copy, and the corresponding source has to be available under the same license. Internal use without a copy leaving the company is a different situation. The list below is the shipping work: what a recipient of that binary can demand, and what you record so a buyer can see it.
You meet OSET-PL-2.1 on a shipped binary when every recipient can get the corresponding source the license describes.
You meet the notice terms when the original copyright lines and the license text travel with the copy.
You keep internal use inside the terms when no copy leaves your company. Distribution is what usually turns the source duty into real work.
The duties named in OSET-PL-2.1
Notice still travels with the copy. On top of that, OSET-PL-2.1 names a source duty. These are the conditions in the text. The how-to above is when they become real work.
Include copyright
Keep copyright notices on distributed copies.
Include license
Give recipients a copy of the license with the program.
Disclose source
When you distribute a binary of a covered work, corresponding source has to be offered in the way the license describes.
Same license
The combined work you distribute has to stay under this license. You cannot close the covered work with a more restrictive grant.
Things to be aware of
- Saying you only use OSET-PL-2.1 on the server, then shipping a Docker image or an on-prem build. Ask the question per artifact you hand out.
- Offering source for the covered package alone when the license asks for corresponding source of the work you shipped.
What the OSET Public License 2.1 does not do
Search results often flatten OSET Public License 2.1 into a slogan. These are the usual misreads. OSET-PL-2.1 is a grant with conditions, not a permission to skip the paperwork below.
- OSET-PL-2.1 is not "permissive with extra paperwork." Change covered files and ship them, and that source has to be available under the same license.
- OSET-PL-2.1 does not erase notice duties. Copyright lines and the license text still travel with the copies you hand over.
How OSET-PL-2.1 differs from nearby licenses
These licenses are often confused with OSET-PL-2.1, but their release duties differ. Each row summarizes what the license requires when you ship. Open the linked page for the full checklist.
- OSET-PL-2.1
- OSET-PL-2.1 is a copyleft grant for election-system software, based on MPL with extra public-purpose terms. Read the exhibit. Not MIT.
- MPL-2.0
- File-scoped copyleft. The MPL files stay open when you ship a binary, modified or not. Your own separate files stay yours.
- EPL-2.0
- Eclipse-family copyleft scoped to each Contribution. It reaches GPL compatibility only when the project designates a Secondary License.
- GPL-3.0-only
- GPL-3.0 keeps the source duty on distributed binaries and adds a patent grant, an anti-lockdown rule for consumer devices, and a cure period.
Common questions about OSET Public License 2.1
Answers to common questions about what OSET Public License 2.1 requires, when its duties apply, and what evidence belongs with a release.
What is the OSET Public License 2.1?
The OSET Public License 2.1 was written for open source election technology. It starts from Mozilla-style copyleft and adds terms aimed at public-sector use. Covered files you change and distribute have source duties. Do not assume MPL-2.0 is a substitute. Store the actual OSET text on the component.
What does OSET-PL-2.1 require when you ship a product?
You meet OSET-PL-2.1 on a shipped binary when every recipient can get the corresponding source the license describes. You meet the notice terms when the original copyright lines and the license text travel with the copy. You keep internal use inside the terms when no copy leaves your company. Distribution is what usually turns the source duty into real work.
Does hosting a product that uses OSET-PL-2.1 trigger extra duties?
Hosting alone usually does not trigger the source duty for OSET-PL-2.1. Shipping a binary, a container, or an on-prem build does. Notice still travels with any copy you hand over.
Does linking to OSET-PL-2.1 force me to open my application?
For strong copyleft such as OSET-PL-2.1, the FSF reads static and dynamic linking as one combined work when you distribute the result. Shipping a binary that includes OSET-PL-2.1 code is the usual trigger. Internal use with no copy leaving the company is a different situation. Read the actual text, not the family nickname.
What is corresponding source for OSET-PL-2.1?
Corresponding source is the source a recipient needs to build and run the same binary, including scripts and interface files the license names. Hosting a repository URL can be an offer. The offer has to match what you actually shipped. SourceTrust records that a person on your team confirmed the offer. It does not publish your source and does not host a mirror.
How is OSET-PL-2.1 different from Mozilla Public License 2.0?
OSET-PL-2.1 asks this: OSET-PL-2.1 is a copyleft grant for election-system software, based on MPL with extra public-purpose terms. Read the exhibit. Not MIT. Mozilla Public License 2.0 asks this: File-scoped copyleft. The MPL files stay open when you ship a binary, modified or not. Your own separate files stay yours. Open the Mozilla Public License 2.0 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 OSET-PL-2.1 for a buyer?
The catalog marks OSET-PL-2.1 as copyleft, so a source offer item appears on the project checklist when the project's distribution context is Distributed binary or Mixed. A SaaS-only project sees no item for it unless the row also carries a network trigger. Nobody ticks the item for you: a person on your team confirms it, and publishing stays blocked until every applicable item is confirmed. SourceTrust does not publish your source and does not host a mirror.
Where do I record OSET-PL-2.1 for a buyer?
The catalog marks OSET-PL-2.1 as copyleft, so a source offer item appears on the project checklist when the project's distribution context is Distributed binary or Mixed. A SaaS-only project sees no item for it unless the row also carries a network trigger.
Nobody ticks the item for you: a person on your team confirms it, and publishing stays blocked until every applicable item is confirmed. SourceTrust does not publish your source and does not host a mirror.
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.