In March 14, 1999 Ethan Galstad released the first version of Nagios. Then, nearly exactly 10 years later (May 2009), Icinga (a fork of Nagios) was born. What happened there? Why a fork? In this article, I will shed some light about what made the Icinga developers decide to fork (although they still send patches to Nagios). In this article, I will talk to both Ethan Galstad himself, and Michael Lübben (one of the founding Icinga team members and Nagios addon developer). I will quote Michael and Ethan in the article.