Edward Naughton, a prominent IP litigator, said in his Huffington Post article on this that he's skeptical of Google's approach because he believes the header material they copied is likely copyrightable. If it's copyrightable, it can't just be relicensed by third parties.
During all those years that Linux has been around, no one other than Google has tried to take this kind of material from the original kernel headers and publish it under any license other than the GPL. And no one has tried to do an alternative glibc. I guess what someone would do is take glibc and fork it on LGPL terms.