For those of you who only use the Japanese (or Chinese) features of this dictionary, there's a MUCH better alternative to this program. Try JEDict. Unlike WordLookup, it allows unlimited search of the two primary dictionaries, even if the program is not registered.
It also allows you to look up individual kanji using a number of different methods, including handwriting input.
It's shareware, but there are no registration nag warnings.
http://www.versiontracker.com/dyn/moreinfo/macosx/14095

I used to use Wordlookup until I found this program. If you're willing to pay for the program, or even if you're not, JEDict is a MUCH better choice.