In the beginning there was spamming. The spamming took place on a swedish forum, hosted by a swedish TV-channel, inspired by an international project called "Big Brother". The year was actually 2006 and trolls were highly active on this forum. In the same time, there was an irc-server that received a load of attacks by proxies.
At this moment, there was a project on the big internet called BOPM (Blitzed Open Proxy Monitor) that has special clients checking on connecting clients to that irc server. Tornevall Networks started to think of migrating a similar solution into web spaces. The problem, that made a huge difference between the IRC and WWW-protocol was the fact that on IRC, you made one connection and then one check against a DNS Blacklist. If it was blacklisted as an open proxy, it got k-lined, akilled in any other form: banned. This was not possible with HTTP-connections, since a check would take place each time a client connected to a website. The idea in this case, was to cache the resolving, into a local storage since DNS-servers otherwise could be overloaded with queries (depending on how DNS caching was made).
Somewhere in may 2006, this project started and the first extension released was actually the rbl-extension at sourceforge, together with an extension for the CMS tool e107 and vBulletin. After this year, 2006, no more suprises happened. Only maintenance jobs. Recently someone has realized that the old projects has became quite obsolete. Deprecation of the old project from 2006 was initiated somewhere between december 2015 and june 2016.