Meta and Nvidia released open-weight AI models this week, available for developers to download for free via the open-source ecosystem, contrasting with proprietary models from OpenAI and Anthropic. Meta unveiled Muse Glimmer on Monday, with CEO Mark Zuckerberg saying the company would open the weights for its latest AI model, Muse Spark 1.2. A day later, Nvidia debuted Nemotron 3.5 Lightning, stemming from its Nemotron 3 family released in December, and said its models are "truly open source" because it publishes training datasets, techniques, and model weights. The releases follow an open letter on July 24 from American tech companies urging policymakers not to place "premature restrictions" on open-weight AI models, even from China. Critics have raised national security risks of Chinese models and the AI training practice called distillation, which can be viewed as intellectual property theft, while leading players contend restricting use would place too much power in the hands of too few companies. The companies face competition from Chinese AI labs like Moonshot AI and DeepSeek, as well as Alibaba's Qwen. Box CEO Aaron Levie, a signatory of the letter, called Zuckerberg's plan for Muse Spark 1.2 a "very big deal" because it rivals top foundation models from Anthropic and OpenAI. The new models are smaller and intended to run on laptops for tasks like powering on-device digital agents.