That doesn't make sense to me at all - you can have a closed source system running on top of Linux, today.

Isn't that exactly what Android is?

edit: misread your comment

No, Android (or rather, AOSP), is fully open source.

Most device makers fork AOSP and distribute binaries containing their modifications. These always come with source code for the GPL portions, and occasionally also the portions licensed under permissive licenses such as Apache and BSD.

For instance, OnePlus and Sony publish these Android sources: https://github.com/OnePlusOSS https://github.com/sonyxperiadev?tab=repositories

> Most device makers fork AOSP and distribute binaries

That's what Google does as well and it's called "Android".

If that was actually Google's intent, then it seems silly to release Fuchsia under any semblance of a free software license.