This Windows programme is a port from an open source application called KDirStat written for KDE running on Linux/BSD/Unix type operating system. In the spirit of open source, One characteristics of being open source is having others extend or provide their own version of the software. For example, altWinDirStat from from WinDirStat with some updates. Its a matter of seeing who can stand the test of time in the open source world.
Wouldn't you agree that it opens up more possibilities and increase access to better software?