From the kernel's COPYING file:

    NOTE! This copyright does *not* cover user programs
    that use kernel services by normal system calls - 
    this is merely considered normal use of the kernel, 
    and does *not* fall under the heading of "derived
    work".

As I read it, the non-Linux part of Android is entirely in user-space, and thus exempt from the terms of the GPL with respect to the kernel.