Free software is a good thing. I wanted to be able to distribute the code under the GNU GPL or the GNU LGPL, so I needed to write a clean-room implementation. I do not resent other people for not releasing their code. They have already given a great deal in describing their own work. Anybody complaining about a copyright license is a whiner.
Implementation is the sincerest form of flattery.
I'm eager to try out their code. If you want to try the programs in this package, you will need a C compiler and make. If you want to plot the munged output of experiments, you will need gnuplot. If you want to read the code, you will need CWEB and TeX to process the .w files into .dvi files. You'll probably also want GNU autoconf and GNU automake.