After a long time trying to find a way to feel good doing what I've been paid to do, finally it's clear on my mind. I don't mind about work with free/non-free software. What moves my motivation is another thing: I only want to do something useful, useful for me, useful for people ... in a large scale. Unfortunately, I didn't have this possibility in any place I've worked for.
Okay, it's time to search for something better ... :)