What does that mean for proprietary drivers for Linux? They aren't shipped with Linux/a Linux distribution, Nvidia doesn't ship any Linux, but they can only be used with Linux.
It means exactly what you think: Linux cannot permit proprietary drivers. Long ago, someone made a thought experiment and predicted what would happen if proprietary Linux drivers were officially allowed: <https://lwn.net/Articles/162686/>
See also: <https://www.kernel.org/doc/html/latest/process/stable-api-no...>