This software for identification and clustering of non-polar contacts in proteins has been described in F. Drabløs, Bioinformatics 15(6), 501-509 (1999). The software is available for download as np_clus.tar.gz, and installation and basic usage is described in a README file, which is also included in the tar file. Make sure that you save the file with the ".tar.gz" extension, some browsers try to change that for some reason. The included binary is for the Cygwin platform, but the source code should compile with most standard C compilers. An awk interpreter and a postscript viewer is also needed for visualisation of the results.
We are working on a new and more flexible version of the np_clus software, where different types of interactions may be investigated. However, no release date yet.