@lembas : this is clear :)
In my post, I was talking about one "positive" point revealed by Stallman
when he say "bring Windows users to GNU/Linux OS".
Yes, Steam on GNU/Linux means considering first convenience, then freedom.
His answer to my previous question is : do not play non free games (so do not
have any PS/Xbox, Steam OS or Windows+Steam). This is quite difficult
considering the video games as a passion for some of us. But yes, this
passion can't be put over our freedom.
It's all about the choice we do.
Thanks to all for your answers. I'm always searching for the "right way" to
manage with FOSS and some of my hobby, and still can't deal with it :/ I need
more courage to stop playing in order to really put freedom over all.