Download the sources from http://developer.berlios.de/projects/radiusclient-ng/
Untar the source tarball:
root@localhost:/usr/local/src# tar xvfz radiusclient-ng-0.5.2.tar.gz
Compile and install the library:
root@localhost:/usr/local/src# cd radiusclient-ng-0.5.2 root@localhost:/usr/local/src/radiusclient-ng-0.5.2# ./configure root@localhost:/usr/local/src/radiusclient-ng-0.5.2# make root@localhost:/usr/local/src/radiusclient-ng-0.5.2# make install