In my experience, information hoarders can be classified into two types: Those who like to share their knowledge and get some sense of gratification from overtly helping others, like myself, and those who don't. Obviously.
Now, both sides have their reasons, and the one that likes to share their knowledge will rarely give it all out for typically the same reason that the one's who don't share their knowledge don't: they are trying to make the people around them better, and in my biased opinion, they are correct in doing so. (of course, you also have those who don't share knowledge simply to make themselves indispensable as well, and that is for the wrong reasons, and they should be done away with as they usually aren't that great to begin with)
After all, they had to delve deep into the arcane and esoteric seas in order to learn what they know, usually through pure experimentation, a liberal application of critical thinking, flashes of intuition and insight, and mystical rites involving various types of sacrificial livestock, and they came out the better for it. The line of thinking usually is that if the people around them are too lazy to or can't manage the same then they shouldn't even be doing the job to begin with, and they certainly aren't worthy of their knowledge. When those around them go through the same things that they had to, then they will come out a better programmer because they will have learned how to think well and solve complex problems and all that.
It's essentially forcing others to become better through strife. While plenty will be trod over and cast out, those who make it through the gauntlet will inevitably be far better than they would have if they became better through cooperation.
Now, as for getting them to share the information: you can't force them to do so. Trying to force them to will make them see you as either greedy, lazy, or too stupid to get there on your own, and they certainly aren't going to take pity on you in any of those cases. If someone higher up attempts to force them to do so they might become very nasty, turning all their considerable intelligence towards thwarting the individual, or even quit outright rather than betray their principles, after all, there are plenty of places that could use their skills and knowledge.
There's really only one way to get one of these that doesn't like to share their knowledge to willingly share their knowledge: become worthy of it. Usually having knowledge that they don't have is enough (but hard to do). Quid pro quo and all that. Otherwise, buy a couple of goats and dive on in.