Functional Source License 1.1 · Apache 2.0 future
A licence written to protect you from us, and us from them. Four clauses, in plain words, and one of them is a promise we cannot take back.
Licence
FSL-1.1-Apache-2.0
Cost, any company size
$0
Converts to Apache 2.0
after 2 years
Charting engine
MIT, today
I
Trade with it, deploy it across a fund, modify it, self-host it, teach with it, research with it, and sell services around it. The one excluded purpose is a commercial product or service that substitutes for Pairlens.
In the licence text
“Permitted Purpose” covers any purpose other than providing a competing product or service.
II
No tiers, no seat counts, no paid features hidden in the code. The only paid thing we offer is the optional hosted Intelligence subscription, which is a convenience and never a gate.
In the licence text
No fee provision exists in the licence at all.
III
An irrevocable grant, already written into the text. If Pairlens is acquired, abandoned, or changes direction, the code you depend on is permanently free and forkable.
In the licence text
“Future License”: Apache 2.0, effective on the second anniversary of the release.
IV
The FSL grants a patent license for your permitted use today, and the Apache 2.0 conversion carries Apache’s well-known patent grant, the reason large institutions trust it. Compliance review tends to be short.
In the licence text
Patent licence granted under both the FSL and the Apache 2.0 future licence.
The irrevocable part
Not a roadmap item, not a pledge: a grant already written into the licence. If Pairlens is acquired, abandoned or changes direction, every release older than two years is permanently free and forkable.
From the day a release ships, its source is public. Read it, run it, fork it, patch it, self-host it, personally or across an entire company, and a patent licence covers that use. The one excluded purpose is selling a competing product built from the code.
On its second anniversary the release converts to Apache 2.0, patent grant included. The clause is already in the licence text, so the conversion does not depend on us still being here to honour it.
SPDX: FSL-1.1-Apache-2.0
FAQ
Plain-language summary, not legal advice. LICENSE.md is what governs.
Yes. The terminal costs nothing, for individuals and companies alike. There are no license tiers, no seat counts, and no paid features hidden in the code. The only paid thing we offer is the optional hosted Intelligence subscription, which is a convenience, never a gate.
The precise term is source-available, sometimes called Fair Source. All the code is public on GitHub and you can use, modify, and self-host it freely. The one restriction (no competing commercial resale) means it doesn’t meet the strict open-source definition for its first two years. After that, each release converts to Apache 2.0, which is full open source by any definition.
Our whole point is to be the free, transparent alternative to the big trading platforms. Under MIT, any of them could take the code, wrap it in their branding, and sell it back to you as a closed product, using our own work to outspend us. The FSL blocks exactly that move and nothing else. We don’t need protection from you, we need it from them.
Yes, expressly. The FSL names internal use and access as a permitted purpose, so deploying Pairlens across a trading desk, a fund, or an entire company needs no license fee and no negotiation. Combined with the patent grants, that tends to make compliance review short.
The license includes an irrevocable grant: two years after a release ships, that release is licensed to you under Apache 2.0. It isn’t a promise we might keep, it’s already in the license text. If Pairlens the project ever disappears, gets acquired, or changes direction, every release older than two years is permanently free and forkable.
Fast Financial Charts, our WebGL2 charting engine, lives in its own repository under plain MIT, commercial use included, no two-year wait. Use it in any app today.
Open it free in your browser, read every line of the source, and know the licence guarantees it stays that way.
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