If you can't force them to specify where they are installing it, it is still fair game to have a config file where they have to list where they installed the app. And if you ship an install.pl or an install.sh script, or package an RPM, it's fair game for you to specify where your stuff gets installed. Sounds like you need to exert a little more control over your users. And then, even then, use absolute pathing versus a relative solution. Relative pathing has it's place, but avoid it when you can.