On the topic of the discussion, no, I do not believe that the CC-BY-NC license is acceptable. This is for one simple reason: it violates at least two of the four essential freedoms of free software (2 and 3). The license adds restrictions on the ways I can share the source code, therefor violating my freedom. Having the freedom to sell programs that you have copies of is fundamental to your right to share them. Of course I am not saying that I would personally try to sell a free software game someone else made and gave away in order to try and make money for myself alone. Not only does that seem like a jerkish thing to do, but it also sounds like a remarkably bad business model. But there are lots of other things I would most likely not do that the four essential freedoms would allow me to do. I almost never actually bother to read the source code of the programs I use, for instance, and I can count on one hand the number of times I have changed this source code for any reason. Practically speaking, I do not need the source code for most programs I use, because I will not read or change it. But just because I do not do this does not mean I should not have the right to do this, of course.
(And just because it may be jerkish for me to try to profit commercially as an individual off of freely available works, that does not imply that there are not totally valid and defensible ways in which a person or an organization might go about selling free software, including games, for money.)
As to what rms has to say about so called "artistic works", I feel he is simply wrong. rms is not a prophet and his words are not gospel, and he can certainly be wrong about stuff like this. The distinction he makes between what is and isn't "practical use" is spurious, as well. After all, what game that could have non-free media could function without it? If I removed all, or even just some, of the non-free images and sounds from the source of a game that had them, would the game even be functional at all anymore if I tried to run it? It might vary slightly on a case-by-case basis, but almost universally the game would lose certain functionality, which means it would become broken without the non-free parts, which means it would not be a free program. Or is the implication that the game itself, as whole, is an artistic work, and should therefor not have to be free? I disagree with that on principal, but also because it implies that games serve no practical purpose. What if you use games for stress relief, or what if they are a component in some sort of therapy? What if they are used for educational purposes? What if you are a professional video game player? After all, there are many ways to make money from playing video games now, from professional competition to Let's Players and other entertainers. Should the people in these professions not use free software for their work? Or, what if I set up a Minetest server and convince the people I work with to join up and have meetings on there. Then a game would be serving a practical, business-related, corporate-approved purpose, would it not?
And even if you just use the game to have fun, who is to say that is not a practical purpose? The point is, this distinction between "practical" and "non-practical" works is largely a pointless one when it comes to computer data. Also, this distinction, as best as I can tell (and I may be wrong, so correct me if I am), is made by Stallman personally, and does not appear to be the official position of the FSF.
I did not really mean to write such a book here, sorry for that.
However, it is difficult to communicate things like this without being wordy.