No, it isn't "clearly a judgement based on motivation". It's not the purpose (read: intentions) of the artist - which is what motivation amounts to - that is in question here, it's the purpose of the particular artwork itself (read: what the work is supposed to realise/achieve).
I only skimmed through the article, but I can certainly sympathise with Ebert's argument that the production process speaks against it being art. If an artist had a marketing team and executive team that give input for the work from the perspective of what would sell, we're likely to call him a phony, or at least we probably wouldn't appreciate his output as true works of art. And why do you think that is? I think that's because his art stops being about subjective expression but more about product design and marketing.
A few things here, how can artwork have a purpose quite different to the intentions of the artist? 'purpose' is a quality that can only be endowed by things with minds; artwork does not have a mind and of course cannot have independent purpose. We are left then with the problem of dividing the intentions of the artist in such a way (that is not uselessly expansive or immediately arbitrary) that we can say an artwork has a purpose which does not relate to all the motivations of the artist.
To consider again the Sistine Chapel, we could easily frame the purpose of the ceiling to be to shelter Michelangelo from papal displeasure. We do not on intuitive grounds; this is not how we instinctively see it. But there is no hierarchy to say this latter interpretation is superior to the former. Similarly we could note that Michelangelo was hardly free in his productive process; from the outset he was restricted to old testament themes with of course certain standards of 'good taste'. He was not given free reign. There is evidence that suggests the entire productive process was overseen be the theological 'advice' of one Aegidius of Viterbo, the validity of this is not decided either way. And yet, our estimation of the Sistine Chapel ceiling does not depend on whether Michelangelo was told what to paint be a theologian; if that were so we would hold of on declaring said ceiling 'art' because we would need to decide the issue one way or another beforehand. We simply don't know the truth of the matter, and for many works of art we never know the truth of such a matter. Indeed the question of 'purpose' need not enter our heads. I'll expand on this later...
Why, yes. Otherwise anything can be art. But we don't find that true, do we?
I'm struggling to think how all this answers the question. By 'art' (as distinct from 'craft') we certainly understand something fairly specific. Unless you mean to say that the term is meaningless anyway, what's wrong with trying to narrow down what exactly we mean by it, which does follow a certain pattern if not a certain set of rules?
Okay, so what do you think they have in common?
Here's the crux; Don't think, but look! Don't say a priori "Art must have some quality in common otherwise we could not call it art, anything could be art",
look to see whether there is indeed anything in common to all.
In art we see not one essential quality that is shared by them all, we see a rich network of interrelation and similarity, such that one piece of art can be related to another piece of art by a number of quite different characteristics, including its relation to a third piece of art. There is a family resemblance in common rather than an essential quality.
We can see when considering art we do not immediately ask 'Does this have the essential quality that makes all art art' and indeed this question may never trouble us at all; in the case of subjective expression certainly we cannot tell rather a piece is the product of an artists subjectivity rather than a producers avarice; such would require an extensive knowledge of the history of the piece. This we do not need before seeing something as art and when the word 'art' is used in language we do not require this essential quality to be made explicit; the narrative required for such a quality to be meaningful (of arts 'purpose' being in the mind when judging art) is simply not in accord with reality.
And this lack of explication does not make the word 'art' meaningless because we use it perfectly well; indeed such a lack has never bothered us before. We cannot draw a fixed boundary to define the concept of 'art' which includes both cave drawings and The Seventh Seal whilst excluding anything 'non-art', and nor do we need to! It does not require a fixed boundary to make the concept of 'art' usable anymore then it requires a definition of the like 'One Metre equals one hundred centimeters' to make the concept of a metre usable. Before definition we may not have an exact measurement but this matters little; Very well, we have an inexact measurement and we can still point out the inexactness in our definition of a metre.
The need to supply a common and essential quality to a concept before this concept is meaningful is illusory, and our perception that such a concept must have such a quality is not based on how words are used in language.
To further illustrate with the example of 'game' (bare-facedly stolen) we would be left answerless if we asked what definition of game includes Chess, Rugby, Solitaire and catch? If we take card games as one group, with all their many points of congruence, and compare them to board games we can see many correlations between the two, but certain common features drop out whilst others appear. And then we might move to ball games and again certain features are retained but much is lost, including much of what was in common between the first two. Do all require skill, are all for amusement or do all involve competition? Certainly solitaire involves no competition and the types of skill involved in chess and cricket seem quite different...
Look then at a game like 'spin the bottle' or 'chinese whispers', here we see the element of amusement come again but many other characteristic features have dropped out...What links Simon Says to professional football? We can go through many different groups of game and see these similarities drop out and re-appear, such that the result of our study is that we see a complex network of crisscrossing similarities, such that one thing can be a game whilst sharing no essential quality with all other forms of game, but rather being similar to other games, but in no set way. There is family resemblance in the family of games, such that there is no essential quality by which we would on sight identify a family , yet we can see that certain members of a family share the same eyes, others the same gait or manner of speech, yet others the same height or hair; these resemblances criss-cross in the same way and by such we can identify a family much like we can identify a game.
And yet it is not so that game is defined by a logical sum of these resemblances, for although I can use 'game' in such a rigidly defined way I can also use it in an expansive way, unbounded by a frontier. Indeed this is how one uses game for the concept is not bounded. Where would we put such a boundary? The usage of the word is not everywhere bounded by rules anymore than in cricket there are rules over how high one can hit the ball, or what to do if a player starts to shoot his opposition. Yet we can still play cricket and cricket still has rules, just like we can still use the term game; again it has never troubled us before that the word 'game' should have no boundary, or if so we know not what that boundary is. As with art new boundaries add nothing to our understanding of the term and there is no need for an essential quality to make either term meaningful, we need family resemblance and naught else. We do not need one common trait in everything to which we refer to as art, and indeed in the case of many concepts such a common trait will be completely absent...