Any kind of knowledge can be expressed by bits. After all even our brain is just made of on/off connections that can be represented as bits. (OK the brain is a bit more complex because the on/off electrical thresholds can vary). And knowledge is a purely non-physical thing (even though our body already has some hard-coded knowledge on how it should work and evolve).
It is interresting to study the theory of information to know what exactly is knowledge and what is not. In short "1+2=3" has some redundant knowledge. Actually "1", "+", "2" is enough to represent 3 and how you can get to this result. The knowledge you get when you remove all the redundancy is called the entropy. And this entropy is usually what we refer to when we talk about knowledge.
So in short, what you have in your brain or that you can write can be represented by digital information (it already is if you write it on a computer). But is there some knowledge that you're not allowed to say ? No (unless you work in a security sector). Is there knowledge that you're not allowed to share ? No (in a free world). Are you allowed to use all your knowledges ? No, because there are laws to govern the interaction between humans. But laws are usually done to protect people from being armed by other people for unfair reasons (and all the subtility is in the meaning of this "unfair"). But the capitalist world has changed this state of things. Companies have become as important as human beings, if not more. And they have become so important that it is now hard to change laws in favour of the community of the whole humanity. But everyone (or most) agrees that it has gone too far.
I think the key change is to free all knowledges. Everything that people build should be free for everyone else to use (the law is there to tell you you should not build bombs, even though governments think they have this right). After all, as I said in this other article, you never know if someone smarter or simply with a different point of view might be able to improve what you have done. It may not be true, but it might be and that's what really matters.
But maybe I'm too much for the ultimate speed of the progress and the situation is not that good. After all, humans are far from perfect. Usually too selfish and too blind to think about everyone instead of themselves. This is actually what has driven progress (increase of knowledge) for so long: the competition, usually driven by sexual matters. But now things are changing. We are entering a global world, where the good and bad influence of what you do is becoming global. And we should start thinking in global terms, even though it's impossible to have everyone agree on anything (or simply some thing).
I have learned hard recently that all knowledge, all informations is not good, and not everybody want to know it. It is actually a big problem. Even if all knowledge was free, some people would prefer not to know (so the sharing system should be opt-in and not opt-out).
Bah, my explanations here aren't so good and I don't have a definite point of view on all these things. Just some feelings that things should change in favour of more sharing. Maybe later I'll have better reasons on why it's good and necessary. But anyway, that's what I'm doing.