the issue is that you can't easily trademark a common word. It's possible (e.g. Apple for computers) but you run into problems. Apple ran into some notorious tr

the issue is that you can't easily trademark a common word. It's possible (e.g. Apple for computers) but you run into problems. Apple ran into some notorious trademark problems. Trademarks don't need to be officially filed to be real in common law -- you just have to use a distinguishing mark for a certain period of time. so the GNU/FSF screen would have rights to Screen in the computer program industry even if they haven't officially filed. Filing just helps you defend a trademark, it's not strictly necessary.