You max use and redistribute OpenRat if you accept the GPL license.
The latest Version is available at dl.openrat.de.
Short installation instructions:
First login with "admin" and "admin". You must change the password at the first login.
Openrat is available as a Debian-package. Insert the following line into the file /etc/apt/sources.list:
deb http://debian.openrat.de/latest ./
An apt-get install openrat does the install. Please check the database settings in file database.ini.php.
See more installation hints.
Feel free to download and use these logos: