Expand licensing info

Author: jayvdb

README.Copyright.txt

@@ -7,3 +7,20 @@ under the new simplified BSD license, approved by the Open Source Initiative (OS
 * http://www.opensource.org/licenses/bsd-license.php
 
 See Copyright.txt
+
+GDCM includes source code from other projects which have different copyright.
+
+This is an incomplete list of additional licenses included:
+
+- BSD-2-Clause and BSD-3-Clause are used extensively (e.g. Utilities/gdcmcharls/License.txt)
+- Apache-2.0 license is used extensively
+- MIT license (e.g. `Source/MediaStorageAndFileFormat/gdcmIconImageGenerator.cxx` and `Utilities/gdcmexpat/COPYING`)
+- OFFIS (e.g. `Utilities/gdcmjpeg/COPYRIGHT.dcmtk`; c.f https://spdx.org/licenses/OFFIS.html )
+- Custom public domain license (e.g. `Utilities/pvrg/COPYING`)
+
+The GDCM library does not include any source code that is:
+
+- GNU General Public License or 
+- GNU Lesser General Public License
+
+However, `Examples/Csharp/MpegVideoInfo.cs` is licensed under the GNU Lesser General Public License.

Utilities/socketxx/COPYING

@@ -3,8 +3,8 @@ Copyright Notice:
 Copyright (C) 1992-1996 Gnanasekaran Swaminathan <gs4t@virginia.edu>
 
 Permission is granted to use at your own risk and distribute this software
-in source and  binary forms provided  the above copyright notice and  this
-paragraph are  preserved on all copies.  This software is provided "as is"
+in source and binary forms provided the above copyright notice and this
+paragraph are preserved on all copies.  This software is provided "as is"
 with no express or implied warranty.