The source code is included when you download ns4decode from the downloads page. It's written in Python. If you have questions about the source code, feel free to ask me (ns4decode@gmail.com).
I made a special Program file that includes a variety of parameter values for regression testing. (The example output file shows the synth settings for that Program.) You may download the regression-test material using the button below. The zip-file contains a single ns4p file, the associated csv files generated by ns4decode, and a text file with the commands to run the regression test. The total size of the zip-file is less than 10 kilobytes.