Personally, since I'm less interested in MS-DOS modes and fixed-length 8bit charset modes, I switched to the redesigned NetHack 4, which works fine with modern UTF-8 terminals.
NetHack 4 is geared towards progression of the game and staying up to date with the changing world rather than mothballing the old game. It's a separate project from NetHack 3.x, with different goals and development teams.
The continued existence of an MS-DOS port doesn't detract from versions for current operating systems in the slightest... Vim and Emacs even maintain current ports for MS-DOS and I doubt anyone is going to give them up just because a DOS port exists.
NetHack 4 is a radical shift for the game, and many of its ideas were incorporated into NetHack 3.6 (the upstream project), I think even its developer was placed onto the devteam for upstream NetHack while maintaining the fork simultaneously. It's a cool project, but NetHack 3.x is the conservative one, both in gameplay and in maintaining ports to operating systems of yesteryear (they clearly aren't against removing them, but they support them when there is at least one person to maintain it).
+1 here. The most significant change of Nethack 4 is to separate game logic into a common library named libnethack[0], so you can write your own interfaces and communicate with server using JSON.
Loosing MS-DOS support is kind of a shame, because there's really no reason the game can't support it, but also because software for MS-DOS is some of the most portable software you can write these days.
DOSBox has accidentally achieved write-once-run-anywhere.
NetHack 4 is geared towards progression of the game and staying up to date with the changing world rather than mothballing the old game. It's a separate project from NetHack 3.x, with different goals and development teams.
http://nethack4.org