I have nedit on a couple machines. Well apparently you have a functional X11 and therefore know how to start it and stop it(X11) with GIMP. Same thing with nedit. Download here
http://ftp.nl.freebsd.org/editors/NEdit/v5_5/executables/
for the MacOSX intel.tar. Double click the tar to open it and the nedit folder will show up(open it) and click on the black executable icon named nedit and X11 will start up as will the nedit editor. And in that same nedit folder is a nedit.html which gives documentation of how to use nedit. You can eventually use the Finder to move the folder to /usr/local/bin where you would enter into Terminal, to start the editor: /usr/local/bin/nedit-5.5-Darwin-i386/nedit
From nedit folder: README
"INSTALLATION
NEdit consists of a single, stand-alone executable file which does not require
any special installation. To install NEdit on Unix systems, simply put the
nedit executable in your path."
Just so you get an idea of what is transpiring.