LibEngsas is a c++ library, which uses Qt-Framework and provides some enhancements. Therefore the hidden usage of KDE is one of the most important topics in LibEngsas. The goal is, to give the programmer a common API, regardless KDE is internally used or not. As an example, EFileDialog is a replacement for QFileDialog, which automatically uses KFileDialog internally, if LibEngsas is build against KDE and QFileDialog if not.
The links for linux distributions are pointing to the distribution specific repository. How this file can be used is explained at the documentation at installation help.