The 'idnkit' is an open source, BSD-like licensed software that
provides functionalities about Internationalized Domain Name
processing standardized at IETF.  Major features that idnkit provides
are as follows.

    * libidnkit
      Core library for IDN processing.
    * libidnkitlite
      Light Weight library for IDN processing. (UTF-8 only)
    * idnconv
      DNS zone / configuration file encoding converter.
    * runidn / idn wrapper
      Dynamic link resolver library for UNIX / Windows.
    * BIND 9 patch
      IDN enhancements for BIND 9 DNS lookup tools.

WWW: https://www.nic.ad.jp/ja/idn/idnkit/download/