Radius stands for Remote Authentication Dial In User Service (From http://en.wikipedia.org/wiki/RADIUS).
A RadiusServer is an WirelessSecurity tool. It is an IdentityManagement server for remote users. See http://www.tech-faq.com/radius.shtml
It is said RadiusServer is "the de facto standard authentication provider", even though it is not the 802.11i standard for WiFi.
- outside of WiFi, what do companies use RadiusServer for? What other commercial/stand packages exist?
The MicrosoftWay implementation is called IAS (Internet Authentication Service ). See more at http://www.isaserver.org/tutorials/ISA2004-RADIUS-Authentication-Web-Publishing-Rules-Part1.html
A GnuProject version can be seen at http://savannah.gnu.org/projects/radius/