The binary distribution of idn wrapper contains a DLL of GNU libiconv software (iconv.dll), which is covered by GNU LIBRARY GENERAL PUBLIC LICENSE (LGPL). You can get the complete source code of GNU libiconv software as well as the source code of idn wrapper from the following place: http://www.nic.ad.jp/en/idn/ The official Web page for GNU libiconv is: http://www.gnu.org/software/libiconv/