Yeah I disagree that the users have to contribute something back. Half the value of a project comes from the users. The other half comes from the developers. If no one uses your software then it's worthless and it wouldn't matter if you spent all day playing video games instead. If someone else does end up using your software and builds a business around it and you don't like it then you should either start a business yourself or alternatively think of your work as returning the favor to all the other open source developers who have worked for free and will benefit from your project directly or indirectly by making proprietary software cheaper.