Building

yum install gcc libpurple-devel glib2-devel

Enabling

Enable the plugin via Tools -> Plugins (Ctrl-U).

SELinux

chcon -t textrel_shlib_t '/home/carlo/.purple/plugins/userserv.so'

sudo semanage fcontext -a -t textrel_shlib_t '/home/carlo/.purple/plugins/userserv.so'