All R source code and source file src/htmltidy.cpp are released under the GNU AGPL license. ---- As per https://github.com/htacg/tidy-html5/blob/master/README/LICENSE.md, libtidy source code is: "Copyright (c) 1998-2016 World Wide Web Consortium (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathematics, Keio University). All Rights Reserved. Additional contributions (c) 2001-2016 University of Toronto, Terry Teague, @geoffmcl, HTACG, and others."" The authors of the libtidy sources also used other source code that is licensed GPL-2. All licenses in the included source files have been left intact. As required by the libtidy copyright notice, the following files are noted as being modified for use in this package: - src/alloc.cpp - src/sprtf.cpp Both of those files have been marked as modified in the license copyright header. ------ xml-viewer is MIT licensed ------ vkbeautify is MIT licensed