Because what is happening is that 'people worry'... and people being as they are, they are capable of worrying about almost anything. Particularly when there is some bedtime-story bogeyman lurking behind the scenes.
If you are worried about lock-in, just ask three questions. Do you have freedom to use the software? to change it? to share your changes with others? If so, you are not 'locked in' to Novell any more than to the FSF, Red Hat, Sun, the University of California or any other copyright holder.