Apsi License

Version 2.0 · 10 November 2026

Licensor: ATEC · Official source: https://github.com/ATECTechnologies/apsi · Official website: https://apsi.dev

A plain-language guide with examples is in the documentation: Licensing. It explains this License but does not change it; if the two ever differ, this License applies.

1. Purpose

Apsi is free to use, and its source code is open so that anyone can learn from it, build with it and improve it. This License keeps three promises at the same time:

Anyone may use Apsi for any purpose, including at work, in companies, in government and in products they sell, without paying.
Nobody may sell Apsi itself, or charge for access to Apsi itself, without a separate written licence from ATEC. Changed versions of Apsi stay available under this License.
The origin is always credited to ATEC.

2. Definitions

"Software" means the Apsi programming language implementation that ATEC publishes under this License: its compiler, interpreter, runtime, standard library, command-line tools, editor extensions, installers, documentation, examples and website source code, and any part of them, in source or compiled form.

"Modified Version" means a work that contains the Software or a substantial part of it, changed or not, including forks, ports, translations into another language, and works that are based on the Software's source code. A Modified Version does not include Your Programs.

"Your Programs" means anything You create with the Software rather than from it: programs and libraries written in the Apsi language, programs converted to Apsi with apsi convert, models You train, data, files and other results Your programs produce, and executables made from Your programs with apsi build.

"Runtime Copy" means an unmodified copy of the Software's runtime and standard library that is included in, or installed together with, one of Your Programs so that it can run (for example inside an executable made with apsi build, a container image, or an installer of Your application).

"Selling the Software" means any of the following, done for money or other compensation:

selling, renting, sublicensing or charging for copies of the Software or a Modified Version;
charging for downloading, installing or accessing the Software or a Modified Version, or placing it behind a paywall or a paid account;
offering the Software or a Modified Version to third parties as a hosted service — for example a paid online Apsi compiler, notebook, playground, IDE, API or package registry — where the Software provides a substantial part of what the customer pays for;
selling a product whose main value is the Software or a Modified Version itself, such as a paid distribution, a paid plug-in that unlocks parts of the Software, or a paid language or compiler built from the Software.

Selling the Software does not include: selling or running Your Programs (with Runtime Copies); using the Software inside an organisation; charging for Your own work, such as development, consulting, teaching, training, support or hosting of Your Programs; or receiving donations, grants or sponsorship.

"You" means the person or legal entity exercising rights under this License. For a legal entity, "You" includes every entity that controls it, is controlled by it, or is under common control with it.

3. Licence granted to You

Subject to the conditions of this License, ATEC grants You a worldwide, royalty-free, non-exclusive licence, for as long as the copyright lasts, to:

use the Software for any purpose, commercial or not, including running it in production;
study the source code and modify it;
make and distribute copies of the Software and of Modified Versions, free of charge;
create, use, sell and distribute Your Programs, including with Runtime Copies;
analyse the Software with any tool, including automated analysis and the training of machine-learning models. Distributing a substantial part of the Software's code, also when a model reproduces it, is distribution under this License.

4. Patent licence

ATEC grants You a licence under every patent claim it can license that would be infringed by using the Software as ATEC published it, for the purposes allowed in section 3. If You, or an entity acting on Your behalf, start a legal claim alleging that the Software infringes a patent, this patent licence ends on the date the claim is filed.

5. Conditions

5.1 Do not sell the Software

You may not engage in Selling the Software without a separate written licence from ATEC (section 11). This applies to the Software and to every Modified Version.

5.2 Credit

Every copy of the Software and every Modified Version that You distribute, in source or compiled form, must:

keep this License and all copyright, licence and attribution notices intact;
say, where users will see it (for example in the README, the "about" screen or the documentation), that it is based on Apsi, originally developed by ATEC, with the address https://github.com/ATECTechnologies/apsi;
say that it was changed, if it was, and by whom.

For Your Programs that include a Runtime Copy, a one-line credit in the program's documentation, licence file or "about" information is enough: Uses the Apsi runtime by ATEC (https://apsi.dev), Apsi License 2.0.

Credit may not be hidden, removed or made misleading.

5.3 Modified Versions stay under this License

Modified Versions may be distributed only under this License, with sections 5.1 to 5.4 unchanged, and with their source code available to the people who receive them at no charge. You may not add terms that take away rights this License gives. This condition does not apply to Your Programs, which You may license as You choose.

5.4 Names and logo

This License does not grant rights to the names "Apsi" and "ATEC" or to the Apsi logo, except to state truthfully where a work comes from as section 5.2 requires. You may not suggest that ATEC endorses, sponsors or certifies You or Your work. A Modified Version must not be presented as the official Apsi; give it a name of its own (for example "X, based on Apsi"). Your Programs may say that they are written in Apsi.

6. What stays Yours

Your Programs and everything they produce belong to You. ATEC claims no rights in them, and this License places no conditions on them other than the credit for a Runtime Copy in section 5.2.

7. Rights the law gives You

Nothing in this License limits what the law allows without a licence, such as fair use, fair dealing, or the exceptions for computer programs in the copyright law that applies to You (in Thailand, the Copyright Act B.E. 2537, including sections 32 and 35). Where such an exception allows more than this License, You may rely on it.

8. Contributions

If You submit a contribution (code, documentation, examples or other material) for inclusion in the official Software, You confirm that You have the right to do so and You grant ATEC and everyone who receives the Software a licence to it under this License. You also grant ATEC a perpetual, worldwide, royalty-free, irrevocable licence to use, change and relicense Your contribution as part of the Software, including under the separate licences of section 11, so that the Software can keep a single licence. You keep the copyright in Your contribution. A contribution You mark in writing as "not a contribution" is not covered by this section.

9. Violations and how to fix them

If You break a condition of this License and ATEC notifies You in writing, Your rights continue if, within 30 days of the notice, You stop the violation and take reasonable steps to correct its effects (for example removing paid offers or adding the missing credit). If You do not, all Your rights under this License end. The first time You are notified about a violation, Your rights are restored as soon as You comply, even after the 30 days. People who received copies from You keep their rights as long as they comply themselves. Section 4 ends patent rights separately.

10. No warranty; limitation of liability

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, ACCURACY AND NON-INFRINGEMENT, TO THE EXTENT THE APPLICABLE LAW ALLOWS. YOU ARE RESPONSIBLE FOR CHECKING THAT RESULTS PRODUCED WITH THE SOFTWARE ARE CORRECT FOR YOUR PURPOSE, IN PARTICULAR IN MEDICAL, SAFETY-CRITICAL, ENGINEERING, LEGAL AND FINANCIAL USE.

TO THE EXTENT THE APPLICABLE LAW ALLOWS, ATEC AND THE CONTRIBUTORS ARE NOT LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR ITS USE. THIS DOES NOT LIMIT LIABILITY THAT CANNOT BE LIMITED BY LAW, SUCH AS LIABILITY FOR FRAUD, FOR WILFUL MISCONDUCT OR GROSS NEGLIGENCE, OR UNDER CONSUMER-PROTECTION LAW THAT CANNOT BE WAIVED.

11. Other licences

ATEC may grant other permissions, including commercial licences for Selling the Software, in writing. Contact ATEC through https://apsi.dev or the official repository. No permission exists unless it is in writing.

12. Third-party components

Parts of the Software that were written by others (for example fonts, icons and libraries in the node_modules, fonts or vendor folders, and the Python packages Apsi uses) remain under their own licences, which are listed with them. This License does not change those licences.

13. Versions of this License

ATEC may publish new versions of this License. Each version of the Software is licensed under the version of this License that comes with it. You may also choose to follow the terms of a later version that ATEC publishes. Versions of the Software released earlier under the Apsi Non-Commercial License 1.0 may, at Your choice, be used under this version instead.

14. General

Governing law. This License is governed by the laws of Thailand, without regard to conflict-of-law rules. This does not take away protection that mandatory law where You live gives You.
Courts. Disputes go to the courts of Thailand that have jurisdiction, including the Central Intellectual Property and International Trade Court, unless mandatory law gives You the right to go to another court.
Severability. If a court finds a provision unenforceable, it is changed to the minimum extent needed to make it enforceable, and the rest of this License stays in force.
Language. This License is written in English. Translations are for convenience; the English text applies.
Entire licence. This License is the whole licence between You and ATEC for the Software, unless You have a separate written agreement with ATEC.

15. Notice to include

Put this notice in the README, "about" information or documentation of every copy and every Modified Version:

Based on Apsi, originally developed by ATEC — https://github.com/ATECTechnologies/apsi
Licensed under the Apsi License 2.0. Apsi itself may not be sold; programs written in Apsi are yours.