Funny you should mention NetHack as the latest version, 3.4.3[0], was released on the 8th of December, 2003. I'd say it's a pretty good call to consider it finished.
there are a ton of forks of nethack, and basically the dev team seems to have disappeared[0], so I wouldn't consider it finished as much as "AWOL".
[0] ok, not really, the nethack4 faq mentions 'The development team who worked on versions 1 to 3 of NetHack (the DevTeam) are still working on it (although there was no real evidence of this until 2014), but they don't release their progress, meaning that the situation is effectively the same as if they'd been doing nothing.'
SporkHack was good for a while, harder than 3.4.3 at least.
Sometimes updates actually make things worse. I like Brogue 1.7.2 a lot more than 1.7.3 for example. You should try that game if you haven't already, it does so many things well!
[0] http://nethack.org/v343/release.html