This is really cool. One little detail I've noticed is that it doesn't seem to apply to private repositories, which seems like a bit of an oversight. The repo I'm checking clearly having an Apache 2.0 license text in the LICENSE file. Just because a particular copy of a repo is private doesn't mean that the code within it isn't still bound by an open source license.

EDIT: Before anyone replies with "Why would you want that?", it's fairly common to stage a project privately on GitHub before publicly releasing it. It'd be nice to see that the license is detected correctly before going public with it. As it is now, I don't know what'll happen until I go public, and my first public commit in the repo may well be fixing up something minor to get the license detected properly.