In my opinion, just like landing pages, it makes most sense to point unused domain names to the place that makes you the most money.
Pointing On2 at company info makes sense. People typing it would be looking for that company info. People typing "duck" are very unlikely to be looking for anything about the old company called Duck so it should go to the money page.
This is obviously a deliberate poking-of-tongues at DDG. http://www.on2.com/ was apparently owned by the same company but leads to an page with information about the buyout.
Pointing On2 at company info makes sense. People typing it would be looking for that company info. People typing "duck" are very unlikely to be looking for anything about the old company called Duck so it should go to the money page.