The Boost license, not the Business Source License. Permissive, and it expressly does not ask for a notice inside compiled binaries.
On this page
What it does
BSL-1.0 is the Boost Software License, used by the Boost C++ libraries and by projects that follow Boost conventions. Do not confuse it with the Business Source License (BUSL-1.1), which is a source-available license with real restrictions on production use. Developers type BSL for both. Boost itself is permissive: use it commercially, modify it, keep your changes closed. One feature is unusual. The license requires the notice with source distributions and expressly not with copies that are solely machine-executable object code.
Details
Two things follow from that carve-out. If you ship only compiled binaries, the license itself asks nothing of you, which is rare and worth knowing. The catalog still records Boost as a notice license, so a component under it needs license text before it counts as live on your page. That is deliberate: your attestation page is a disclosure document for buyers, not a minimum-duty calculation. The name collision with BUSL is the other real risk, because it produces wrong answers in procurement questionnaires.
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 BSL-1.0 requires when you ship
When a copy that includes BSL-1.0 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 terms when you distribute source, including C++ headers, and the Boost license notice is included in that source.
You have nothing further to do under the license when your copies are solely compiled object code, because the notice condition expressly excludes that case.
You are on solid ground listing Boost in your notices file anyway. Most vendors do, it costs one entry, and buyers expect the full inventory.
You have answered a procurement questionnaire correctly when your paperwork says Boost Software License 1.0 and not Business Source License.
You keep the same position after modifying the code, and your own changes may stay closed. Boost has no reciprocal duty of any kind.
The duties named in BSL-1.0
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
- Writing BSL when you mean BUSL-1.1. One is permissive, and the other restricts production use until the terms convert on a set date.
- Reading the object-code carve-out as permission to leave Boost off your disclosure list. The license and your buyer are asking different questions.
- Expecting a patent grant like the one in Apache-2.0. Boost does not mention patents, so an express grant is not part of what you get.
What the Boost Software License 1.0 does not do
Search results often flatten Boost Software License 1.0 into a slogan. These are the usual misreads. BSL-1.0 is a grant with conditions, not a permission to skip the paperwork below.
- the Boost Software License 1.0 does not require you to publish your own source. Combining it with closed code is the point of the grant.
- the Boost Software License 1.0 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 BSL-1.0 differs from nearby licenses
These licenses are often confused with BSL-1.0, but their release duties differ. Each row summarizes what the license requires when you ship. Open the linked page for the full checklist.
- BSL-1.0
- The Boost license, not the Business Source License. Permissive, and it expressly does not ask for a notice inside compiled binaries.
- 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.
- Zlib
- Permissive, and built into games, firmware and mobile apps. Three conditions: do not claim you wrote it, mark altered versions, keep the notice in source.
- BUSL-1.1
- Source available, not open source. Each version converts to an open license on its own Change Date, usually four years after release.
Common questions about Boost Software License 1.0
Answers to common questions about what Boost Software License 1.0 requires, when its duties apply, and what evidence belongs with a release.
What is the Boost Software License 1.0?
BSL-1.0 is the Boost Software License, used by the Boost C++ libraries and by projects that follow Boost conventions. Do not confuse it with the Business Source License (BUSL-1.1), which is a source-available license with real restrictions on production use. Developers type BSL for both. Boost itself is permissive: use it commercially, modify it, keep your changes closed. One feature is unusual. The license requires the notice with source distributions and expressly not with copies that are solely machine-executable object code.
What does BSL-1.0 require when you ship a product?
You are meeting the terms when you distribute source, including C++ headers, and the Boost license notice is included in that source. You have nothing further to do under the license when your copies are solely compiled object code, because the notice condition expressly excludes that case. You are on solid ground listing Boost in your notices file anyway. Most vendors do, it costs one entry, and buyers expect the full inventory. You have answered a procurement questionnaire correctly when your paperwork says Boost Software License 1.0 and not Business Source License. You keep the same position after modifying the code, and your own changes may stay closed. Boost has no reciprocal duty of any kind.
Does BSL-1.0 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 BSL-1.0 in a product I ship?
Attribution for BSL-1.0 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 BSL-1.0?
No. BSL-1.0 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 BSL-1.0 dependencies count?
Yes. The condition follows the code, not the package you chose by name. If the lockfile pulled in BSL-1.0 transitively and you distribute that tree, those notices travel too. Listing only direct dependencies is how teams miss the duty.
How is BSL-1.0 different from MIT License?
BSL-1.0 asks this: The Boost license, not the Business Source License. Permissive, and it expressly does not ask for a notice inside compiled binaries. 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 BSL-1.0 for a buyer?
The catalog records BSL-1.0 as a notice license, so a component under it needs license text before it counts as live on your page. That holds even though the license lets you skip the notice in object code. Auto-fetch normally supplies the text from the published artifact. Packages that vendor a handful of Boost headers often ship no license file of their own. A not found result is then common, and you paste the text in yourself.
Where do I record BSL-1.0 for a buyer?
The catalog records BSL-1.0 as a notice license, so a component under it needs license text before it counts as live on your page. That holds even though the license lets you skip the notice in object code.
Auto-fetch normally supplies the text from the published artifact. Packages that vendor a handful of Boost headers often ship no license file of their own.
A not found result is then common, and you paste the text in yourself. Read /docs/reviewing-component for the review flow.
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.