Vibecarbon Is Fair Source

The vibecarbon CLI ships under FSL-1.1-MIT: free to use and build from source for anything that isn't a competing product, converting to MIT two years after each release. The code it generates for you is MIT from day one. Here's exactly what that means, stated straight.

Vibecarbon is licensed Fair Source, under FSL-1.1-MIT. We want to say precisely what that means, because licensing is one of those places where vague language costs you later and honesty costs us nothing.

The short version, the one we use everywhere a directory or a form asks:

Fair Source (FSL-1.1-MIT). CLI converts to MIT two years after each release; generated project code is MIT.

The rest of this post unpacks that sentence.

What you can do

Almost everything. You can read every line of the CLI, build it from source, run it, modify it, and use it to create and operate as many applications as you want, commercial or not. There is no seat counting, no telemetry gate, no feature held hostage behind a hosted service. The source is on GitHub, and what you see is what runs.

The one thing the license reserves is competing with vibecarbon itself: offering the CLI, or a substitute for it, as your own product. If you're building your SaaS with vibecarbon, none of this touches you. It only touches someone whose product is vibecarbon.

Your application is yours, outright

This is the part that matters most and gets skipped most often in licensing posts: the code vibecarbon generates for you is MIT from day one. The application scaffold (the React front end, the Hono API, the database migrations, all of it) lands in your repository under a plain MIT license the moment vibecarbon create finishes. Open Source Templates, no asterisk.

Sell the app. Sell the company. Fork the scaffold beyond recognition. Stop using vibecarbon entirely and keep every line. The license on our tool was never a lien on your product.

Every release becomes MIT

Fair Source licenses carry a built-in expiration on their one restriction. Under FSL-1.1-MIT, each vibecarbon release automatically converts to plain MIT two years after it ships. Not "we promise to relicense someday." The conversion is written into the license text itself, and no future decision of ours can take it back.

That's the structural answer to the question every source-available license should have to answer: what happens if the company behind this loses interest, gets acquired, or disappears? With vibecarbon, three things are already true before you ever ask. Your generated code was MIT from the start. Your infrastructure, code, and data are self-contained and under your control, so nothing stops serving when a vendor has a bad quarter. And the CLI you depend on becomes MIT on a schedule nobody can cancel.

Why not just call it open source?

Because it isn't, and we'd rather lose the label than earn it dishonestly.

The Open Source Definition doesn't allow restrictions on competing use, so FSL-licensed software is not open source, full stop. Plenty of companies blur this line, and the developers who notice, correctly, stop trusting everything else those companies say. We'd rather tell you the truth and let the terms speak for themselves: source you can read, build, and modify; freedom to use it for anything except cloning our business; and a two-year fuse on the single restriction.

We think that's a fair trade to keep vibecarbon funded, maintained, and improving at full speed. Sentry, which created the FSL and stewards the Fair Source movement alongside Keygen (with adopters like Liquibase and Tuist) made the same call for the same reason: sustainable software needs a business model that doesn't fight its own source availability.

The fine print, in plain sight

License: FSL-1.1-MIT, in the repository root.
Applies to: the vibecarbon CLI and its services.
Does not apply to: anything vibecarbon create generates for you. That's MIT, in your repo, from the first commit.
Converts: each release becomes MIT exactly two years after it ships.
Questions: open an issue on GitHub. Licensing questions are welcome there, and we answer them in public.

If you're evaluating vibecarbon and the license is the thing you're unsure about, that's a reasonable place to be unsure. Read it. It's short. And if something in it would genuinely block how you want to build, tell us. We chose Fair Source because it's the most honest way we know to build this in the open while still being here to maintain it in ten years.