Android (as a Linux descendant)
termIT supportprogramming
The most widely deployed Linux system in the world, and a deliberate piece of licence architecture: the copyleft kernel underneath, a permissively licensed framework and a purpose-built C library above it, so manufacturers can ship proprietary layers without publishing them.
The arrangement is legal, effective and expensive in a way that took a decade to show. Device makers kept large kernel modifications out of the mainline tree, so shipping a security update meant rebasing a private fork - which is a direct cause of the update problem that left phones unpatched. Later work to upstream that support and stabilise the module interface is an attempt to pay down a debt the original boundary created. The general lesson: where you draw the licence line becomes your maintenance burden.
Also known as: bionic, aosp, out-of-tree kernel, generic kernel image