Source Code was found at http://files.chatnfiles.com/carousel/019A/ (as described in 019A.txt from there).

"This seems to be the definitive version of the Hack 3.x series." PC Hack 3.6
PC Hack 3.6 Source Code Part 1 of 2
PC Hack 3.6 Source Code Part 2 of 2
Another Source Code Package from http://avrc.city.ac.uk/nethack/source/hack361s.zip from http://avrc.city.ac.uk/nethack/source.html