The Aspell Indonesian dictionary is based on the MySpell One:

  Indonesian spell-checker and hyphenator for OpenOffice.org
  Version 1.0 - 19-02-2004
  Version 1.1 - 06-04-2004
  Archives id_ID.dic, id_ID.aff and hyphen_id_ID.dic were created from
    scratch by
  Author: Benitius Brevoort <benitius.brevoort@kapusin.org>
  Copyright (c) 2004, held by Author
  under the terms of the GNU General Public License.

Original MySpell README file and affix file can be found in the doc/
directory.
