Moonshot AI has publicly accused AI code editor Cursor of using its Kimi K2.5 model without adhering to licensing terms. The allegation was sparked by developer @fynnso, who identified the model ID for Cursor's Composer 2 as "kimi-k2p5-rl-0317-s515-fast," strongly suggesting the incorporation of Kimi K2.5.
Technical Evidence Points to Reuse
Yulun Du, head of pretraining at Moonshot AI, confirmed the tokenizers matched and questioned Cursor's compliance with licensing fees. The model is released under a modified MIT license, which requires commercial products with significant user bases or revenue to prominently display "Kimi K2.5."
Cursor's Silence and Product Updates
Notably, Cursor's March 19 release of Composer 2 highlighted performance improvements through continued pre-training and reinforcement learning but omitted any mention of Kimi K2.5. The company, valued at $29.3 billion, has yet to respond to the allegations. Analysts warn that if proven, the violation could result in substantial damages and reputational harm.
The Gray Area of Open-Source Licensing
This dispute underscores the compliance challenges in open-source AI model usage. The modified MIT license adds restrictive clauses, but enforcement of "prominent display" and "user scale" remains ambiguous. Moonshot AI has stated it reserves the right to take legal action to protect its intellectual property.