It is important to clarify that (Numeric Taxonomy and Multivariate Analysis System), often referred to as NTSYS-pc, is a legacy software package for numerical taxonomy, cluster analysis, and ordination. It is not open-source software ; it was commercial software (originally by Applied Biostatistics Inc.).
You will find a legal “free download” for the full, unrestricted NTSYS-pc for molecular data unless the copyright holder has explicitly released an old version as freeware (which they have not, to my knowledge).