<+elohim> from what I've heard other people yap about, /usr is for OS installed software. but I have not actually looked over FHS because I don't really believe it's relevant.
<+elohim> you can put shit wherever you want, as long as your system is set up properly it will work. I don't need some ruler weilding nun sitting around waiting to smack my nuckles because I put a game in /games instead of /usr/games