Open source in the AI age: open weights vs open source AI, training data, and the community

One of six themes that emerged from the EOLE 2026 online kick-off workshop (25 June). Background: see the kick-off topic.

Why it matters for sovereignty. AI was called the elephant in the room: most systems will soon embed AI, and if sovereignty is about autonomy, control and the capacity to decide, dependence on third-party AI cuts directly against it. AI also strains the classic open source promise (read, audit, rewrite) when models are opaque.

What came up at the workshop. A key distinction: open weights are not the same as open source AI. Open-weights models are free to use but give no visibility on training data, which is fine for a large share of applications; truly open source models remain few (Apertus, Allen Institute’s OLMo, Hugging Face initiatives) and are not yet seen as frontier. Open-weights models, including Chinese ones, were credited with breaking the proprietary stranglehold. Two “no-no’s” were named from the OSAID experience: use restrictions (Llama-style conditions, including bans on generating synthetic data to prevent forks), and AI as a service, meaning dependence on hyperscalers: you only use open stuff when you control it and it runs on your machines. Attention was also drawn to the heavy subsidies behind proprietary frontier models, and to a gap Europe could fill: an open, continuously extended corpus of training data, notably for post-training and reinforcement learning. A deeper question was left open: what is the role of the community when a large share of code is AI-generated (quality assurance? data curation? and what future for junior developers)?

What already exists to build on. OSAID (Open Source AI Definition); EuroLLM and EU open-model initiatives; open and open-weights models (Mistral, DeepSeek, Llama with caveats, Apertus, OLMo, Hugging Face); the open data agenda.

Open questions. How do sustainability, access and transparency need to be rethought for AI-based stacks? Can Europe build an open training-data commons, especially for post-training? What are the concrete consequences of Llama-style licence limits? What is the community for in an AI-assisted world?

How to contribute. Reply below with analyses, model reviews and initiatives, ideally by end of September 2026. Rapporteurs welcome for the Barcelona event (November 2026): volunteer by replying below or by direct message on this forum. Possible outputs: an “open weights vs open source AI” explainer and a mapping of EU open models and open training-data initiatives.

Hello all,

Several developments in 2026 bear on the questions above. The discussion continues on Friday 27 November 2026 at Universitat Pompeu Fabra, Barcelona (registration is free, see EOLE 2026 – EOLE).

On the definition of open source AI, G7 digital ministers approved on 29 May a “Vision on AI openness opportunities and shared language”, developed with contributions from the OSI. In its typology, the open source AI category admits exceptions to publishing training data only where sharing is legally or technically impossible, with information about the missing data to be provided: https://opensource.org/blog/open-source-initiative-helps-g7-deliver-vision-on-ai-openness

On licences, Meta launched Muse Spark in April through hosted services, then released Muse Spark Open weights on 15 October under the Muse Model License, which includes commercial restrictions. A fresh case for the third question: Introducing Muse Spark Open, The Most Capable US Open‑Weight Model to Date | Meta AI Research

On data, Common Corpus 2.5 from Pleias (19 February 2026) holds about 2.27 trillion tokens described by the producer as public domain or permissively licensed, with 33 languages above one billion tokens: Pleias

On AI-generated code, two opposite choices this summer. Debian’s general resolution “LLM usage in Debian” (vote closed 28 August) adopted “Responsible Use of Generative AI”, which neither endorses nor prohibits these tools and keeps the contributor responsible: General Resolution: LLM usage in Debian. GCC’s policy of 29 July declines legally significant contributions containing or derived from LLM-generated content, with limited exceptions, and requires an Assisted-by tag otherwise: GNU Compiler Collection - AI Policy - GNU Project

For those who have trained or fine-tuned models: has anyone done post-training on a dataset limited to public domain and permissive sources such as Common Corpus, and with what result?

Benjamin, for the EOLE committee