You just copy the files in your joomla component folder (after backing up the original folder first ofcourse) and you are good to go. Excellent work!
Joomla 3.3.3 + Mosets 3.5.5
Thank you very much for your review.
1) You've right. This is not a plugin, it's some files that users have to overwrite the core files of mtree's template. But in jext there isn't any option to publish folder or files so I called this files as a plugin.
2) If you extract the zip file, you will find a documentation inside. There is a "readme.txt" file that describes how you can use this.
3) This is free, for greek people and they knows how to use it, so, where is the problem? Have you use this extension or you want to destroy the image of this extension? I don't think that you are from Greece and you have used this (plugin).