According to Jim Melvin the following are obsolete:

ext/plugin/build/solaris/license.txt
ext/plugin/build/solaris/LICENSE
ext/plugin/build/solaris/license_dialog.html
ext/plugin/doc/license.txt
ext/plugin/doc/license_ja.txt
ext/plugin/doc/license_en.txt
ext/plugin/src/share/converter/license.txt

The last of these makes it into the build (it winds up in the HTML converter).
Please delete these obsolete files: they cause confusion whenever it's
time to update the real license files. If there are any other obsolete
files in those directories, this might be a good time for some Spring
cleaning.