'license' directory. in windows package

[Tatsuro M. <tma...@ya...>]

In README-Windows.txt on windows package for 5.5 branch,
I found the decription

Licenses of these runtime libraries can be
  found in the 'license' directory.

zip or 7z archives does not have license directory
installer have license directory but it has only gnuplot copyright.

I have forgotten how license of other libraries were treated.
Those should be prepared in license direcory in extradist?

Thank you for advance.

Tatsuro