"Knowledge is important."
Translation:Viden er vigtigt.
I was wondering about this too. Check out http://en.wikipedia.org/wiki/Danish_grammar under the section "Infinitive and verbal nouns."
Viden isn't exactly a common noun since the -en isn't a postpositive article, but according to this Wikipedia reference, in the case of verbal nouns like viden :
the verbal noun governs the common gender.
So it looks like you're right. Team Danish?
I wondered the same thing, so I just asked my good friend Ingerlise who is Danish. She explained that you can say it either way, but if you say Viden er vigtigt, you are talking more about the topic of knowledge rather than just knowledge in general, such as if you said Viden er vigtig. So by using the neuter form of vigtigt you emphasis the importance of having knowledge.
I'm not familiar with Swedish, sorry. It's just that in this context "knowledge" is not referring to a specific subject. Kendskab is more specific, awareness of something/knowledge about something. Viden is not specific, and can be seen as a synonym for "being educated".