"Open weights, not open source" is the distinction most coverage gets wrong. Models like DeepSeek, Qwen, and Kimi K2 release downloadable weights, often under permissive licenses, but that is a different thing from the open-source software definition, which also expects the source and the ability to rebuild from scratch.
Why it matters: open weights let a company self-host a capable model, fine-tune it on private data, and run it without sending anything to a vendor. The license still governs commercial use, and some are "modified" (Kimi's K2-family license, for example, adds an attribution requirement once a product crosses very large usage thresholds). Always read the model card rather than trusting the "open source" label, which is applied loosely across the industry.