I used nmap a lot during the 2.5 days (c. 2001), and was even a (very occasional) contributor as they were porting to Windows. I can safely say I have 0 idea how 90% of its functionality works anymore - and I think that's a testament to how far the project has come.

It was best of breed then, and is up there with the most successful open source projects - certainly in the security space, but maybe even anywhere.

Hats off to Fyodor and the rest of the team. This looks like really excellent work.