Current version: ESOL v2.1 | Jurisdiction: Germany (Berlin) Maintainer: @VolkanSah & @BadTin and some Cats
ESOL is a usage license that is added on top of a base license (MIT, Apache 2.0, and others). The base license governs copying and modification of code. ESOL governs the ethical and legal use of the Work: no fraud, no weapons, no unauthorized security operations, no parasitism, and no AI training for closed-source models without consent.
Status note: Licenses with usage restrictions do not meet the Open Source Definition (OSI, point 6). Software under ESOL is "source available" or "ethical source", not "Open Source" in the strict sense.
Everyone may use the code, also to train open models (public weights under a free license). Training of closed models needs written consent. Text and data mining for closed-model training is reserved (Art. 4 Directive (EU) 2019/790, § 44b UrhG) and declared in ai.txt. Assistive Use stays free. Crawlers cannot check whether a model will be open, so ai.txt disallows automated crawling; open-model trainers rely on the license. Note: robots.txt only works at the root of a domain, GitHub does not serve it for repositories, so the license text and ai.txt are the reservation here.
| Version | File | Status |
|---|---|---|
| 2.1 | ESOL_v2.1.md | Current |
| 2.0 | ESOL_v2.0.md | Original release, archived unchanged. Releases published under 2.0 remain under 2.0. |
What's new in v2.1
- Back to the voice of v2.0, including the Psychological Barrier (Section 5)
- One single, consistent document (the 2.0 text contained contradictions between Section 1 and Section 4)
- AI training for Closed AI Systems is prohibited without written consent, training of Open Models is allowed; Assistive Use (prompting an AI assistant on your own project) stays allowed
- New definitions: Output, Contribution, Assistive Use; contributions are licensed under the base license plus ESOL, contributors keep their attribution
- Two-tier termination: severe violations (4.1 to 4.6) end the license immediately, others (Section 3, 4.7) get a 30-day cure period
- Public documentation (Wall of Shames) only for substantiated violations and, for curable ones, after notice and an opportunity to respond
- Authorization wording no longer contradicts Section 2 and 4.5; defensive security research is expressly possible
- German law references updated and marked informational
See CHANGELOG.md for details.
How to apply ESOL to your project
Copy ESOL_v2.1.md into your repository root and add this to your LICENSE or README.md:
This Work is licensed under the [INSERT BASE LICENSE, e.g., MIT] together with the
Ethical Security Operations License (ESOL v2.1). Both apply cumulatively.
The ESOL is a mandatory, non-severable condition of use.
By using this software, you agree to all ethical constraints defined in ESOL v2.1.
File header identifier: ESOL-2.1
Only the copyright holder can apply ESOL to code. You cannot add it to third-party code.
Compatibility with base licenses
This is a practical overview, not legal advice. ESOL always needs a base license, because it does not replace one.
| Base license family | Combination with ESOL | Notes |
|---|---|---|
| Permissive: MIT, BSD, ISC, Apache 2.0, Zlib, and similar | Works | You may add terms to your own distribution. The result is no longer OSI-"Open Source". |
| Copyleft: GPL, LGPL, AGPL, MPL, EPL, EUPL, CDDL, OSL, and similar | Generally not possible for third-party code | These licenses forbid or allow removal of additional restrictions. Only usable for code you own entirely. |
| Creative Commons (BY, SA, NC, ND) | Not recommended | CC 4.0 forbids additional terms that restrict the granted rights. CC also advises against use for software. |
| CC0, Unlicense, Public Domain | Only for your own new or modified parts | A dedication cannot be re-restricted for the original work. |
| Proprietary / no license | ESOL alone does not grant copy or modify rights | Add a base license that does. |
Maintained for the community by @VolkanSah | Wall of Shames