The plugin is valid:
Plugin Name: Gallery2 Integration
Plugin URI: http://wpg2.ozgreg.com/
Description: Integrates WordPress users, theme and single sign to Gallery2.<br/> Documentation, Support Forums.
Author: Ozgreg with CSS design by Marc Lorenz
Author URI: http://www.ozgreg.com/
Past code, invaluable design & help, thanks to John Arnold
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
It just doesn't show up. I've upgrdaed to the latest WP, although it only shows 1.5 in the dashboard; I'm assuming this is OK?