LICENSES/README: expand text to summarize state for binaries and libs

LICENSES/README: expand text to summarize state for binaries and libs

We would say how *sources* are licensed, but actually most user care about the
resulting binaries. So say how the *binaries* are licensed. I used the word
"effectively" because the permissive licenses don't set any requirements on the
binaries, so the license of sources is a complex mix, but the resulting
binaries have a simple effective license.

Also, make it clear that the GPLv2 license applies to udev programs, but not
the shared library. Based on private correspondence, there's some confusion
about this.

(cherry picked from commit bd7236912f373e0a06a1b0395000ec67d96767af)