I read the "Why do this project" section on the site, and am not convinced. Nagios is a very actively maintained project, and did have major features added about a year and a half ago. It is totally suited for use in large installations, especially with the help of existing third party enhancements like GroundWork Monitor. And on the non-issue of wanting a flexible Nagios, a lack of flexibility is NOT one of Nagios' problems. It is insanely flexible, and has tons of add-ons and plugins. Also being in C, it performs very well, especially the current version. I've looked at the code, and it's not bad - maybe the shinken authors are just intimidated by C.