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Why Kitsune Tools is MIT Licensed

We considered CC BY-NC, GPL, and MIT. Here's the full reasoning behind choosing MIT — and what open source actually means.

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Why Kitsune Tools is MIT Licensed

Before v0.2.0, Kitsune Tools had no license file. That sounds harmless — the code was on GitHub, anyone could read it. But in legal terms, no license means all rights reserved. Nobody could fork it, copy a snippet into their own project, or contribute back without technically infringing copyright. The opposite of what this project is for.

So I picked a license. Here's the full thinking.

What I actually wanted

Three things:

  1. Attribution. If someone uses this code, I want my name to stay on it.
  2. Freedom to use. I don't want to make it hard for students, educators, or other developers to build on top of these tools.
  3. No legal weight on contributors. The license shouldn't require a lawyer to understand.

What I didn't particularly care about: stopping companies from using it commercially. The tools are physics simulators. If a company wants to embed a pendulum demo in their product and credits Kitsune Tools, that's fine. That's exactly the kind of reach I want.

The licenses I considered

CC BY-NC 4.0 — Attribution + NonCommercial

This one is tempting on the surface. It sounds protective. You have to credit me, and you can't sell it. What's not to like?

The problem: CC BY-NC is not an open source license. The Open Source Definition, maintained by the Open Source Initiative, has ten criteria a license must meet. Criterion number six explicitly states:

The license shall not restrict anyone from making use of the program in a specific field of endeavor.

"No commercial use" violates that directly. A project under CC BY-NC is source-available — people can read the code, but they can't freely use it. That's a meaningful difference.

Beyond the definitional issue, CC licenses aren't designed for software at all. They don't address patents, they have no concept of compilation or linking, and the legal language is written for creative works like music and writing. Applying CC to code creates ambiguity that nobody wants.

GPL v3 — Copyleft

GPL is genuinely open source. It's used by Linux, Git, and thousands of major projects. The core mechanic: if you distribute a modified version of GPL software, you have to open-source your modifications under the same license. It's self-perpetuating openness.

For a project like this, GPL would mean: if you fork Kitsune Tools and ship your own version, your code has to be public too. That has real protective value against corporations quietly taking the project and making it proprietary.

I seriously considered this. But for a toolkit of interactive physics tools, it felt heavier than the actual risk. The pendulum simulator is not the kind of thing a Fortune 500 company is going to steal and lock up. The copyleft clause mostly adds friction for the small developers and students who are the actual audience here.

MIT — Permissive

MIT is two paragraphs. It says: do whatever you want with this, keep the copyright notice, don't sue me if it breaks. That's it.

Attribution is baked in — the license notice with my name has to stay in any copy or substantial use. Commercial use is permitted. Derivatives don't have to be open source.

It's the most widely used open source license in the JavaScript ecosystem for a reason. NPM is full of MIT packages. The friction to use, contribute to, and build on MIT code is essentially zero.

Why MIT won

The goal of this project is for people to learn from it — the tools, and the code behind them. A restrictive license works against that goal. MIT maximises the chance that a student, educator, or developer can pick up this code and do something useful with it without stopping to check whether their use case is allowed.

The attribution requirement means the project still gets credited wherever it ends up. That's the only protection I actually cared about.

If the project eventually grows to the point where copyleft starts making sense, that's a conversation for a future major version. For now, MIT is correct.

What this means for contributors

If you open a pull request and it's merged, your contribution is MIT licensed. No CLA, no contributor agreement, no legal overhead. Your code is in the project under the same terms as everything else.

The license file lives at the root of the repository. It's short enough to read in under a minute.

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