Meta is back in the open-weight AI arena, this time with a large model and a list of conditions.
On October 15, Meta released Muse Spark Open, calling it “the most capable US open-weight model to date”. It made the model’s weights available for developers to run on their own hardware.
A developer can download it, change it and build a product without paying a licence fee, but selling access to the model comes with a few conditions.
Meta built the model for coding and AI agents, with 816 billion parameters, the values a model learns during training, of which 42 billion are active at a time. The model can process up to 1 million tokens in a single request, giving it the room to work with large information.
Developers can download the model from Hugging Face and cloud platforms or use it through providers such as Groq and OpenRouter. Meta says developers can also run it across two Apple Mac Studios with M5 Ultra chips, allowing local usage.
The $20-million condition
Meta describes its licence as carrying “limited commercial terms, which allow many developers to use the model for free”, while setting rules on how they can use it.
The company allows developers to change the model, train it for specific tasks, use it to train other models and share or sell copies, as long as they follow the licence.
The main commercial restriction applies to companies that offer AI models as a service, giving customers model outputs through an application programming interface (API) or a similar interface.
If a company and its affiliates together make more than $20 million in gross revenue over any 12-month period, it must notify Meta and sign a separate written agreement before offering Muse Spark Open or models derived from it.
Also read: Meta’s new Muse AI agents raise questions about privacy and user control
It is important to note the threshold covers a company’s total revenue, including money made from activities over and above hosting Muse Spark Open.
However, the restriction does not apply to internal use, research or commercial activities outside the model service category, such as using the model for features in a company’s own product.
Meta’s name travels with the model
Products using Muse Spark Open must prominently display “Built with Muse Spark Open” in their interface, documentation, website or settings menu, according to the licence.
The rule also covers other models that developers create, train or improve using Muse Spark Open, including those learnt from its outputs.
This means a startup could train another model on data generated by Muse Spark Open and still have to display Meta’s notice in products using that model.
Also read: Meta launches frontier AI models under Muse series; here’s the lowdown
Open weights, not open source
“Open” has different connotations in AI, depending on the freedom a model’s licence gives the developers. Open weights means developers can download and run a model, while the Open Source Initiative’s definition of open-source AI requires freedom to use it for any purpose without permission.
Meta’s requirement that certain businesses sign a separate agreement fails that test.
Earlier, too, Meta imposed limits on its Llama licences, setting a threshold of 700 million monthly users. For Muse Spark Open, many mid-sized AI businesses could cross the prescribed threshold.
China’s DeepSeek, released under the MIT licence, takes a different approach with V4.1 Flash. It has no revenue threshold or product branding requirement, but users must keep the copyright and licence notices when sharing copies.
Artificial Analysis, an independent benchmarking platform that evaluates and compares AI models, gives both models a score of 39 on its Intelligence Index, but their licences give developers different levels of freedom.
For most developers and early-stage startups, Meta’s terms should still allow them to fine-tune the model and build products without paying the company, provided they follow the licence requirements, including adding the required label.
The restriction matters more for cloud and GPU providers that want to host the model and sell API access. Once a provider’s group revenue exceeds $20 million in gross revenue over any 12-month period, it needs a separate written agreement with Meta to offer Muse Spark Open through that business.