applied the changes Cédric advised

debian/changelog

 ruby-cssminify (1.0.2-1) UNRELEASED; urgency=medium
 
-  * Team Upload
   * Initial release (Closes: #982260)
 
  -- Klaumi Klingsporn <klaumikli@gmx.de>  Fri, 20 Nov 2020 11:44:41 +0100

debian/control

 Source: ruby-cssminify
 Section: ruby
 Priority: optional
-Maintainer: Debian Ruby Extras Maintainers <pkg-ruby-extras-maintainers@lists.alioth.debian.org>
+Maintainer: Debian Ruby Team <pkg-ruby-extras-maintainers@lists.alioth.debian.org>
 Uploaders: Klaumi Klingsporn <klaumikli@gmx.de>
 Build-Depends: debhelper-compat (= 13),
                gem2deb (>= 1),
@@ -22,6 +22,6 @@ Depends: ${misc:Depends},
          ${ruby:Depends},
          ${shlibs:Depends}
 Description: CSS minification with YUI compressor, but as native Ruby port
- The CSSminify gem provides CSS compression using YUI compressor. Instead
+ The CSSminify library provides CSS compression using YUI compressor. Instead
  of wrapping around the Java or Javascript version of YUI compressor it uses a
- native Ruby port of the CSS engine. Therefore this gem has no dependencies.
+ native Ruby port of the CSS engine. Therefore this library has no dependencies.
\ No newline at end of file

debian/copyright

@@ -12,7 +12,7 @@ License: BSD-3-clause
 
 Files: debian/*
 Copyright: 2020 Klaumi Klingsporn <klaumikli@gmx.de>
-License: GPL-2 
+License: Expat
 
 License: Expat
  Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -57,46 +57,3 @@ License: BSD-3-clause
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  SUCH DAMAGE.
- .
- On Debian systems, the full text of the BSD license can be found in the file
- `/usr/share/common-licenses/BSD'.
-
-License: GPL-2
- 1. You may copy and distribute verbatim copies of the Program's
- source code as you receive it, in any medium, provided that you
- conspicuously and appropriately publish on each copy an appropriate
- copyright notice and disclaimer of warranty; keep intact all the
- notices that refer to this License and to the absence of any warranty;
- and give any other recipients of the Program a copy of this License
- along with the Program.
- .
- You may charge a fee for the physical act of transferring a copy, and
- you may at your option offer warranty protection in exchange for a fee.
- .
-  2. You may modify your copy or copies of the Program or any portion
- of it, thus forming a work based on the Program, and copy and
- distribute such modifications or work under the terms of Section 1
- above, provided that you also meet all of these conditions:
- .
-    a) You must cause the modified files to carry prominent notices
-    stating that you changed the files and the date of any change.
- .
-    b) You must cause any work that you distribute or publish, that in
-    whole or in part contains or is derived from the Program or any
-    part thereof, to be licensed as a whole at no charge to all third
-    parties under the terms of this License.
- .
-    c) If the modified program normally reads commands interactively
-    when run, you must cause it, when started running for such
-    interactive use in the most ordinary way, to print or display an
-    announcement including an appropriate copyright notice and a
-    notice that there is no warranty (or else, saying that you provide
-    a warranty) and that users may redistribute the program under
-    these conditions, and telling the user how to view a copy of this
-    License.  (Exception: if the Program itself is interactive but
-    does not normally print such an announcement, your work based on
-    the Program is not required to print an announcement.)
- .
- On Debian systems, the full text of the GNU Lesser General Public
- License version 2 can be found in the file
- `/usr/share/common-licenses/GPL-2'.