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.