The program is citeware. That means you don’t have to pay anything for it but if you use it in your work you have to cite it. If you want a custom made adaptation of the program to do something o need my help for the analysis of your data, feel free to contact me. However, please understand that I don't make custom programs or analysis without a full scientific collaboration.
VICENTE VILLARDÓN, J.L. (2014). MULTBIPLOT: A package for Multivariate Analysis using Biplots. Departamento de Estadística. Universidad de Salamanca. http://biplot.usal.es/ClassicalBiplot/index.html