Comment by grapheneos

OS components don't need to have compatible licenses if they're separate from each other. The Linux kernel is GPLv2-only which forbids GPLv3 licensing. That doesn't mean GPLv3 code can't be used in a Linux-based OS.

We use GPLv2 and permissive licensing for GrapheneOS to avoid more restrictive licensing than the AOSP. We'll happily use GPLv3 and AGPLv3 for components outside of GrapheneOS if we think it's the best fit for specific projects. We aren't currently licensing anything as GPLv3/AGPLv3 but we aren't strictly opposed to it outside of the OS.

We'll use what we think are the best open source licenses for what we want to achieve. What we want to achieve is usually broad adoption of our code with painless usage of it. That means we usually choose permissive licenses. We use GPLv2 in certain cases such as Vanadium where we decided we wanted extensions to our code to be under a compatible open source license instead of a source available license or GPLv3.