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Source-availableLicenseRef-MARC27-SA-1.0v1.0

MARC27 Source-Available License

Inspect, evaluate, and research — but no commercial use, redistribution, or derivatives without a written agreement. Source-available, not open source.

Steward: MARC27

This is a source-available license, not an open-source license. The source may be read, audited, and evaluated, but it is not OSI open source: commercial use, redistribution, and derivative works require a separate written agreement. Publishing under it does not place the work in the public domain or oblige any related work to be open.

At a glance

Identifier
LicenseRef-MARC27-SA-1.0
Version
1.0
Status
Current
Effective
February 2026
Steward
MARC27
Type
Source-available
Raw text (.txt) for citation

The MARC27 Source-Available License lets anyone read, audit, and run the software for evaluation and non-commercial research. It does not grant commercial use, redistribution, or the right to create derivative works without a separate written agreement. Publishing under it makes the source visible and citable without placing it in the public domain or making it open source — which is exactly why it suits work that is still in development or kept proprietary.

Permissions

  • View & inspect source
  • Run for evaluation
  • Non-commercial research
  • Security audit

Conditions

  • Keep proprietary notices
  • Contributions licensed back to MARC27
  • Written agreement for anything more

Limitations

  • No commercial use
  • No redistribution
  • No derivative works
  • No warranty
  • Revocable

Definitions

Software
The source code, object code, documentation, and any associated materials covered by the license.
Non-Commercial Research
Academic research, personal learning, and evaluation that does not directly generate revenue.
Source-available
The source can be read, audited, and run, but reuse rights are limited — distinct from open source, which must permit unrestricted use including commercial.

What each section means

1 · Definitions

Fixes the precise meaning of “Software” and “Non-Commercial Research” so the grant and the restrictions can’t be read ambiguously.

2 · Grant of Rights

You may view, inspect, audit, and run the software for evaluation and non-commercial research. The grant is non-exclusive, non-transferable, and revocable.

3 · Restrictions

Without a written agreement you may not use it commercially, redistribute it, create derivative works (other than contributions back), or remove notices.

4 · Contributions

Anything you contribute back is licensed to MARC27 under these terms, plus a broad grant letting MARC27 reuse and relicense your contribution.

5 · Commercial Licensing

Commercial use, redistribution, or rights beyond this license are available by separate agreement — contact team@marc27.com.

6 · No Warranty

The software is provided “as is,” with no warranties and no liability for any claim or damage arising from its use.

7 · Termination

Breaking any term ends the license automatically, and you must destroy your copies of the software.

How it compares

AspectMARC27-SAPermissive (MIT/Apache)Source-available (BSL/PolyForm)Proprietary
Read & audit sourceYesYesYesNo
Run for evaluation / researchYesYesYesNo
Commercial useBy agreementYesRestrictedBy agreement
RedistributionNoYesRestrictedNo
Derivative worksContributions onlyYesRestrictedNo
Converts to open sourceNoAlready openSometimes (BSL)No
OSI-approved open sourceNoYesNoNo

Frequently asked

Is this an open-source license?

No. It is source-available: the code can be read, audited, and run for evaluation and non-commercial research, but commercial use, redistribution, and derivative works require a separate agreement. OSI open-source licenses must permit unrestricted use including commercial — this license intentionally does not.

We published an early snapshot under MIT / CC-BY. Does that force the rest of the work open?

No. MIT and CC-BY are permissive, not copyleft — they carry no share-alike obligation and bind only the specific files released. Later, more complete versions can ship under this source-available license, and foreground work that builds on them is not required to be open.

Who can grant commercial or production rights?

MARC27, the steward and rights holder. Contact team@marc27.com for commercial, redistribution, or project-specific grants.

Can software under this license be declared as Background IP in a funded or ESA project?

Yes. It is declared as proprietary background IP — visible and citable, made available to partners for evaluation and integration, with commercial or foreground terms set by separate agreement. It is not open source and carries no third-party IPR.

Why not just use a standard open-source license?

Because the complete framework is still in development and kept proprietary. A standard open license would let anyone, including competitors, use it commercially. This license keeps the work inspectable and citable while protecting it.

What it covers

  • — Complete or in-development frameworks (e.g. the full KC-UKF estimator)
  • — PRISM Rust crates and the Ink frontend
  • — Any artefact intended to be visible and citable but not open source

How to reference & apply

Cite this license by its identifier LicenseRef-MARC27-SA-1.0 and link to its canonical page marc27.com/licenses/marc27-source-available-1.0.

Source-file header

// SPDX-License-Identifier: LicenseRef-MARC27-SA-1.0
// Copyright (c) 2025-2026 MARC27 — Source-available, not open source.
// Full terms: https://marc27.com/licenses/marc27-source-available-1.0

For an IP / BIPR declaration

Type of Licence: Proprietary — MARC27 Source-Available License v1.0 (not open source). No third-party IPR. Full terms: https://marc27.com/licenses/marc27-source-available-1.0

Full text

Raw .txt
MARC27 Source-Available License
Version 1.0, February 2026

Copyright (c) 2025-2026 MARC27
All rights reserved.

1. DEFINITIONS

"Software" means the source code, object code, documentation, and any
associated materials covered by this license.

"Non-Commercial Research" means academic research, personal learning,
and evaluation that does not directly generate revenue.

2. GRANT OF RIGHTS

Subject to the terms of this license, MARC27 grants you a
non-exclusive, non-transferable, revocable license to:

  a) View and inspect the Software for evaluation, security audit,
     and non-commercial research purposes.
  b) Run the Software internally for evaluation and non-commercial
     research purposes.

3. RESTRICTIONS

You may NOT, without prior written agreement from MARC27:

  a) Use the Software, or any substantial portion thereof, in a
     commercial product or service.
  b) Redistribute, sublicense, sell, lease, or otherwise transfer the
     Software to third parties.
  c) Create derivative works based on the Software for any purpose
     other than contributing improvements back to the original project.
  d) Remove or alter any proprietary notices, labels, or marks on
     the Software.

4. CONTRIBUTIONS

Contributions submitted to the project (e.g., via pull request) are
licensed back to MARC27 under the same terms, with an
additional perpetual, irrevocable grant to use, modify, and
sublicense the contribution under any license.

5. COMMERCIAL LICENSING

For commercial use, redistribution, or modification rights beyond
what this license permits, contact:

  MARC27
  Email: team@marc27.com

6. NO WARRANTY

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED. IN NO EVENT SHALL MARC27 BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY ARISING FROM THE USE OF THE SOFTWARE.

7. TERMINATION

This license terminates automatically if you violate any of its terms.
Upon termination, you must destroy all copies of the Software in your
possession.

Commercial licensing

For commercial use, redistribution, or rights beyond this license, contact team@marc27.com.