Images info:
1. ./ajax-loader.gif, ./ajax-loader-bb.gif are generated by http://www.ajaxload.info/. 
   There is the following statement on http://www.ajaxload.info/: "Generated gifs are totally free for use"
2. ./tree/folder.png, ./tree/folder_go.png are taken from silk icon set (http://www.famfamfam.com/lab/icons/silk/)
   They are released under Creative Commons Attribution 2.5 License.
3. ./window/help.png, ./window/messagebox_critical.png, ./window/messagebox_info.png, ./window/messagebox_warning.png are from Crystal Project (http://everaldo.com/crystal/)
   They are released under GPL License, but I do not know which version: http://everaldo.com/crystal/?action=license
4. The topbar for panels and winsows is slightly modified element from the image taken from here: http://www.bittbox.com/freebies/free-vector-web-page-elements-part-2/
   I have not found anything about license there.
5. The res of images is made by me.