I need using radius with owncloud, i write radius support! :)
It is an extension to app "user_external". http://owncloud.org/support/custom-user-configuration/
This plug-in contains "Pure PHP radius class", a PHP class to connect to RADIUS. This sofware is Copyright (c) 2008, SysCo systemes de communication sa
To install copy user_external into /var/www/html/owncloud/apps/
Insert into config/config.php this config:
'user_backends'=>array(
array(
'class'=>'OC_User_RADIUS',
'arguments'=>array("SERVER", "REALM", "SECRET")
)