As I said, Voluntarily means you actually have choice.
I can voluntarily buy and play Halo 3.
I cannot voluntarily play Halo 3 on the Xbox 360. Because the 360 was only platform it was available for, I was obligated to buy one in order to play Halo 3.
If you voluntarily bought Halo 3, you already knew it was for Xbox 360 unless you're an ill informed consumer and don't understand the concept of exclusives
Thus you are aware of what you're doing and thus agree with it
If you didn't, you wouldn't buy the game
That's not forcing you to do anything you don't want to do, since at any point you can say "no" and not do it
Key thing to note here being, is that the consequences of not doing something here, are just that you don't get to play the game - a concept that's been around since the dawn of time. This is not a new thing, exclusives
But I can see the point you're trying to convey, which is that all games should be available anywhere anytime without restriction because you disagree with the concept of exclusives. To make an exclusive is to take away your choice of platform and creating an "obligation" you don't want
You want absolute choice. And I suppose neither or us are wrong in terms of how we view what a choice is (since viewing something as voluntary or as an obligation is a matter of subjective interpretation. I like my job, thus it doesn't feel like I'm obligated to do the tasks at hand, despite if I don't do them I get fired and lose my job. Your argument there is that doing that job is not voluntary because of the obligation is order to keep the job. My point is, feeling obligated and being obligated are two different things. Related, yes, but different in the sense that if you don't feel obligated, you feel free, like you're making your own choice)
Though if you really want to think about your definition of voluntarily doing something, we are obligated to live. We don't have a choice to live because somewhere down the road we are obligated to drink water or eat food in order to live. Nothing we do in life is actually voluntary as there is an obligation somewhere making whatever choice we make, actually not so voluntary
Examples: I am obligated to breathe, drink and eat in order to live
I make a choice to get a job, but I am obligated to work to their standards or I lose the job
I make a choice to live in a city, but I am obligated to pay money in order to do so which requires me to get the job that I choose which see example two
I make a choice to buy a game, but I am obligated to get a system which can play it, whether it be an Xbox, PS, Nintendo, or PC
I make a choice to buy an exclusive game, which makes me obligated to get a particular system
All of these are choices, but all of this end with an obligation to do something. Does that make them all inherently not a choice?
Doing something voluntarily is best described as doing something while being aware of the obligations that it carries with it. Otherwise, you can choose not to accept the obligations that your choice carries with it, and thus you don't choose to buy the game, work that job, or live your life