MIT is the licence you put on a utility library. Z.ai put it on 320 billion parameters.

GLM-5.3-Flash has 320 billion total parameters with 18 billion active, a 1 million token context, and costs $0.15 in and $0.50 out per million tokens. The weights are MIT licensed, which is about as few conditions as a release can carry: use it commercially, modify it, redistribute it, no revenue gate, no acceptable use annex.

Why this one is different

Open weights usually are not open licences. Llama ships under a bespoke community licence, Qwen3.8-Max under a custom one with a $50M revenue gate, and most of the rest under Apache 2.0 with a use policy attached. MIT is the permissive end of the spectrum, and putting it on a frontier-scale mixture of experts removes the last legal reason a company might have preferred a closed model it could get an indemnity on.

Open weights usually are not open licences.

How we got here

1. 2023 to 2024Llama establishes open weights as a category, under a licence that is not an open source licence.
2. Aug 2025OpenAI's gpt-oss models arrive under Apache 2.0, and permissive licensing becomes a competitive lever rather than a principle.
3. 14 Aug 2026GLM-5.3 is announced, post-trained from the 5.2 base, with weights following on the 27th.
4. 26 Aug 2026GLM-5.3-Flash ships MIT licensed at 320B, and goes straight to the top of the Hugging Face trending list.

What it does and does not mean

A licence is not a guarantee of anything else. MIT says nothing about training data provenance, nothing about whether the weights can be served in a given jurisdiction, and offers no warranty or indemnity, which is exactly what a cautious legal department asks for first. What it does remove is the licence itself as an objection, and for a class of buyer that has been the blocker rather than the capability.