https://github.com/sailfishos

Also the Linux license does not require you to open source your product, this is why a huge chunk of Google Android is closed source and distributed separately from its open source components.

You only need to open-source modifications and kernel side code (drivers, etc). There is a clearly defined boundary in the license (syscall exception) that makes it crystal clear that proprietary applications can use the kernel as long as they are only touching the user-space API headers