GNU Radius is a RADIUS server and an accompanying set of monitoring utilities. It features MySQL and PostgreSQL interfaces for authentication and/or logging (the ODBC interface allows you to use almost any existing DBMS for that purpose), the ability to rewrite RADIUS requests from various NASs to normalize them to a more understandable format, and the ability to completely customize the behavior of RADIUS authentication and accounting based on NAS and user attributes.
SMRadius is a high performance pre-forked RADIUS AAA server. It features a highly configurable backend engine supporting flexible data specifications. Its primary goal is to provide an extremely flexible authentication platform which may serve a large number of industries, including ISPs and WiSPs.