Monolingual is a program for removing unnecessary language resources from Mac OS X.
Monolingual seems to be broken for Mavericks. It worked great on my older Mac Pro work computer which is on Lion, but I get the same "Monolingual is damaged and can't be opened. You should move it to the trash" error message on my personal Macbook Pro running Mavericks. It deleted 1.5GB of unneeded crap off of my work computer, and I need the space here. Please fix!