Closed-weight and open-weight models

The tradeoffs between hosted closed-weight models and downloadable open-weight models — access, what "open" really covers, licensing, cost, privacy, control, and customization. Defines closed- and open-weight precisely, separates open-weight from open source, works through the buy-vs-host cost break-even, compares privacy and license terms, weighs frontier capability against customization, gives decision criteria for each, and shows how one system can use both behind a provider-neutral contract.