SORBL is antispam tool to auto-learn own dnsbl zone. Written on Perl.
Currently using: sendmail (I have no other MTA's logs now;)), rbldnsd, host (bind-tools). Also required any (bayesian) filter (I use spamassassin) in milter mode.
SORBL look for sendmail (sm-mta) messages about relay and about adding "X-Spam-Status: Yes" header, analyse IP/hostname/rDNS info, based on plugins and keep blocked ip list in file for rbldnsd daemon.
nordns - filter senders without rDNS;
iphost - ip-based names like: 188.8.131.52.in-addr.arpa. IN PTR 99-88-77-66.dsl.cool-isp.com.
Unlike standard "no-rDNS hack", for example, this way more liberal - IP will blocked only after first spam message. Also may be used spamassassin dnsbl feature - to help bayes auto-learning.
Ohloh computes statistics on FOSS projects by examining source code and commit history in source code management systems. This project has code locations but that location contains no recognizable source code for Ohloh to analyze.