I got it to work with this configuration.
1) In the beans.xml file:
<security:IdentityImpl>
<s:modifies/>
<security:authenticatorName>jaasAuthenticator</security:authenticatorName>
</security:IdentityImpl>
<security:jaas.JaasAuthenticator>
<s:modifies/>
<security:jaasConfigName>drools-guvnor</security:jaasConfigName>
</security:jaas.JaasAuthenticator>
2) Remove the security-seam and install the new security-seam
rm WEB-INF/lib/seam-security-3.0*.jar
wget https://community.jboss.org/servlet/JiveServlet/download/772921-70585/seam-security-3.2.0-SNAPSHOT.jar
mv ./seam-security-3.2.0-SNAPSHOT.jar WEB-INF/lib
3) Zip the new drools and deploy to the server
4) (optional) In the standalone.xml, y changed the user and role files, so i don't give access to regular users to the designing platform. I'm not really sure if this affects security at all, but it seemed logical
<security-domain name="drools-guvnor" cache-type="default">
<authentication>
<login-module code="UsersRoles" flag="required">
<module-option name="usersProperties" value="${jboss.server.config.dir}/designer.user.properties"/>
<module-option name="rolesProperties" value="${jboss.server.config.dir}/designer.roles.properties"/>
</login-module>
</authentication>
</security-domain>