- lib/html2text.inc from jon@chuggnutt.com, GPL license
- lib/{enriched,icl_commons,imap,mime,utf7}.inc from IlohaMail project, GPL license
- lib/encoding/*.map from Unicode, Inc., with "BSD-lite" license
+ - debian/patches/xss-fix.patch contains code from Squirrelmail, GPLv2
All licenses can be found in the corresponding source file.