The SAB starts the commentary on chapter 11 with a comment using the "Science and History" icon, the issue being that it is generally understood that varied languages did not appear in the world all at once, but gradually over time. Linguistics is an interesting study, and partly because my older sister had studied it in college, I've always had some interest in it. I'm not sure what methods are used to decide how old a language is; as far as linguistic history, most of what I do know is confined to a general understanding of how linguistic lineages are determined. It's fascinating to me the way that linguists can find the similarities that show that most of the languages of Europe, along with many languages of Iran, Pakistan, India and Nepal all are descended from a common linguistic ancestor that probably was spoken somewhere in the Middle East. I've heard some people speculate that all these languages being related is a sign that the Babel narrative is true, and while I suppose it's a possibility, a big problem in my mind is the fact that Hebrew itself is not part of this language family.
While of course at the time of Noah, seeing as they were only eight people who were closely related, there probably was one single language, I do consider this first verse, along with others in this chapter, to be possible hyperbole. After all, the Bible does have a few cases of clear hyperbole: verses where it says "And so-and-so was the richest man that ever lived," or "And so it remained thus until this day." In the former case, one really can't make a claim like that without knowing the future; I tend to suspect Bill Gates has more money than Solomon did. In the latter case, it has to be understood that the writer is referring to up until the time he was writing the story, certainly not up until the time the story is being read, 2-3,000 years later. Getting back to the point here, I wonder if possibly not the whole earth was speaking the same language at the time of the building of the tower, but perhaps a large portion thereof. In any case, the time scale is not fully 100% clear on where this story is meant to fit into history. Also, as with the creation story, God may have made an appearance of many years of language evolution that didn't actually occur, but I can't think of any good reason for that, so chalk that up to wild speculation on my part.
In verse four, a decision is made by the people of Babel to make a tower to reach Heaven. Although the SAB objects on scientific grounds (I assume), the Bible at no point says that this is a project that has any chance of succeeding. (Although it would be impossible to build a tower that would reach to "Heaven" as in the dwelling place of God, I wonder if it would be possible to build a tower that reached into outer space, assuming you had unlimited resources. The meaning of "heaven" is not completely clear here.) While they may have thought that they did have a chance of making it, it's fairly clear that their real purpose is to create a sense of self-importance and notoriety.
So God comes down to see the tower. This is an odd passage, and the SAB places it and many like it on the page questioning God's omniscience. This is something about God that I can't quite fathom, frankly. Doctrinally, Christians and Jews understand God to be omnipotent, omniscient, and omnipresent, but there are times when the Bible portrays God in ways that appear to contradict those attributes. In cases like this and Genesis 18:21, I believe the sense that's being conveyed is not that God does not know what's going on, nor that He's not already there in the plain of Shinar, but that since something important is going on, He's taking a moment to really fully turn His attention on it. While it's essentially figurative speech, I think there's a literal sense to it, as in the latter case, it appeared that God did physically come down to earth to deal with Sodom and Gomorrah. I suspect God was a physical presence in Babel as well.
So God does this because, as the SAB says, God is worried. However, He's not worried for exactly the reason that is cited. There is no threat to God, but there is a threat to God's order and plan for the human race. God intended the human race to spread out and cover the earth, and He did not intend them to become self-important. He notes that the more they all team up together, the more they can accomplish, but they're not accomplishing the things they were meant to accomplish. Thinking that they can get to Heaven simply by building a tower is a grave misunderstanding of the nature of Heaven and the personality of God. In a later chapter in Genesis, we'll see a structure that does reach from the earth to Heaven, and its significance.
So anyway, God figures that the best way to stop this building project and put a little humility in these folks is to make them all unable to understand each other. I actually recently had heard a sermon that touched on the subject that every time in the Bible that people find themselves against their will in the midst of people who are talking unintelligibly, it's a sign of God's disfavor upon them. Here, it's quite obvious that that's what's going on.
Finishing up this story, there are a few lingering questions about the nature of God. Whether God is singular or not is an item I already addressed, and won't go over here, since I think it was well-covered at that point. On the other hand, the SAB asks a very compelling question, straight out of ICorinthians: "Is God the author of confusion?" While I think I have what may be an adequate answer for this case, I have to admit in my weakness for honesty that I think the SAB could have bolstered its case with far more examples than this, such as ICor 1:27 (EDIT: I see the verse has since been added.) and a few choice O.T. passages in which battles were won by God confusing Israel's enemy. Those might be harder to deal with.
In one sense, there may be a misunderstanding of the passage in ICorinthians. The context is about people getting confused because they're all trying to talk at once in church rather than one at a time. Taking this into account, one might make a good case that God allows confusions for His enemies, but not for His children. On the other hand, dealing with this particular passage in Genesis, there are a few things worth noting. It can be said that these people were already confused. They were rebelling against God's wishes, which is not generally a wise thing to do, and they were attempting a task that was impossible. God didn't make them confused as much as change their confusion to another sort. It could also be said that the word here is not "confuse" but "confound", and while "confuse" seems to be a popular choice for translating this Hebrew word "balal", the KJV word choice is suggestive of something more straightforward; that is, that God didn't so much confuse them, but frustrate them. They probably still could get by, but it became much more difficult to deal with their neighbors and get things done on a communal scale. So they got the hint and quit the project.