Let's list them, scripts (actively developed/released publicly):
Wakaba http://wakaba.c3.cx/ (Perl)
Kusaba X http://kusabax.cultnet.net/ (PHP)
Orphereus http://orphereus.anoma.ch/ (Python)
PyIB https://github.com/tslocum/PyIB-Standalone (Python)
Kotoba http://code.google.com/p/kotoba-ib/ (PHP)
TinyIB https://github.com/tslocum/TinyIB (PHP)
Ochan http://code.google.com/p/ochan/ (Java)
Wakarimasen http://git.kiace.com.ar/wakarimasen.git/ (Python)
In addition to >>126 list:
Pixmicat! http://pixmicat.googlecode.com/ http://pixmicat.openfoundry.org/ (PHP)
Derived from Futaba, has template engine and modular architecture, internationalization (English(US), Chinese(Taiwan) and Japanese), wrappers that enable switching data source, file storage method and thumbnail maker
Another addition to >>126 list:
Kakaha http://code.google.com/p/kakaha/ (PHP)
Uses SQLite; download: http://code.google.com/p/kakaha/downloads/list?can=1&q= installation: http://code.google.com/p/kakaha/wiki/Installation