Il existe pour RadicalSpam 2 types de licences :
RadicalSpam : Licence EUPL (compatible GNU v2) - http://osor.eu/eupl [Wikipedia]
Amavisd-new : Licence GNU v2 - http://www.ijs.si/software/amavisd/LICENSE.txt
SpamAssassin : Licence Apache v2.0 - http://www.apache.org/licenses/LICENSE-2.0.html
Clamav : Licence GNU v2 - http://www.gnu.org/copyleft/gpl.html
Razor : Licence Artistic - http://razor.sourceforge.net/artistic.php
DCC : Licence spécique DCC - http://www.dcc-servers.net/dcc/dcc-tree/LICENSE
Postgrey : Licence GNU v2 - http://www.gnu.org/copyleft/gpl.html
Postfix : IBM PUBLIC LICENSE VERSION 1.0 - http://www.opensource.org/licenses/ibmpl.php
Python : Python Licence - http://www.python.org/download/releases/2.4.2/license
liste des licences OpenSource - http://www.opensource.org/licenses/