[Plugin: Multiple Category Selection Widget] Does not work : results are not filtered at all

First the choice “all” is not seen by the widget when you choose it in the admin settings.
Secoundly, when you let it choose by users, the “and” (traduction of “all”) appears in the result’s url but it doesn’t work !
In fact, this plugin is broken (see other posts since one year in this forum).
Agence web Aheli (France)

http://wordpress.org/extend/plugins/multiple-category-selection-widget/