This software uses license "GPL v.2". It means for example you may get its source code and modify as you want in your project. This license is one of mostly progressive and grants you ability to have the best flexibility ever.
For example if you want to change behaviour of your site's menu in very special (unique) way, you may easely do it. Code you get when buying product has good quality and may be used by programmer who adopts is to the site.