The source code to htool and the HeNCE execution libraries comes in the same package. In order to build htool, your workstation must have X windows version X11R4 or X11R5 and the Athena Widget Libraries installed.
A compiled htool program may be used with an X display server (either a workstation or an X terminal) that supports version 11, release 3 or later functionality. The X window system may be obtained via anonymous ftp from x.org.