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▸ EXPLAINER

What does "open source" mean for software and AI?

By PixPause Editorial · Updated September 26, 2026 · 4 sources

SHORT ANSWER

Open source software publishes its source code under a license that lets anyone use, study, change and share it. For AI it is murkier: many "open" models only release their weights (the trained numbers) under restrictive licenses — often called "open weights" — which is not the same as open source.

EXPLAIN IT LIKE I'M 5

Open source is a recipe anyone can read, cook and change. "Open weights" is a finished cake you're allowed to take home — but not the recipe, and with rules about who can eat it.

How open is "open"?
◀ ClosedFully open ▶
  1. Closed: use it only through the company's app or API
  2. Open weights: download and run the model, under the vendor's licence (e.g. Llama)
  3. Open source: code, weights and training-data details, free to use and change

Positions are categories, not scores.

Open source software

With open source software you can read the code yourself, which is why it matters for trust: privacy and security claims can be checked instead of taken on faith. Examples on PixPause include the Signal messenger and coding tools like Aider, Cline and Continue.

Open source AI vs open weights

An AI model is more than code: it has weights (the parameters learned in training) and the data it was trained on. In October 2024 the Open Source Initiative published the Open Source AI Definition 1.0, which requires the code, the weights and sufficiently detailed information about the training data to be available under terms that let anyone use, study, modify and share the system.

Many popular "open" models do not meet that bar. Meta's Llama license, for example, restricts some uses and requires companies with more than 700 million monthly users to ask Meta for permission; the OSI has said the Llama license is not open source. Releasing downloadable weights is still genuinely useful — you can run the model yourself — but "open weights" is the more accurate label.

Why it matters to you

Open code means outsiders can spot problems — and sometimes a company open-sources an app after being caught, as happened with ZCode. Open weights mean you can run a model offline, on your own device, without sending data to the vendor.

▸ THE HYPE VS WHAT WE FOUND

Real claims involving this term, each checked in a PixProof with linked sources.

"Our app respects your privacy."ZCode silently uploaded whole workspaces to its maker's cloud; after it was exposed, Z.ai open-sourced the app and removed the upload code.QUESTION ITZCode PixProof →"An open-source model runs locally with strong accuracy."Laya does run offline on Apple Silicon, but early testing found significant accuracy drops versus larger hosted models.QUESTION ITlaya PixProof →

▸ PIXPROOFS THAT USE THIS TERM (12)

▸ COMPANIES BEHIND IT

Meta Platforms, Inc.Signal Technology Foundation

HYPE OR REAL?

"After ZCode was caught uploading whole workspaces, its maker open-sourced the app and removed the upload code."

▸ QUICK QUESTIONS

Is Llama open source?
Meta calls it open, but its license adds usage restrictions, and the Open Source Initiative says it does not meet the open source definition. "Open weights" is the more precise term.
What are open weights?
The trained parameters of an AI model, published so anyone can download and run the model — without necessarily sharing the training code, data, or open-source-style usage rights.

▸ SOURCES

Spot something wrong? Tell us — corrections are logged, see methodology.

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