wordnet and freebase are both very large and very complementary open-licensed databases, and connecting them together will enable the creation of very intelligent software.
because this requires 'connecting the meanings', and not the words, automatic reconciliation (atleast in the beginning) is far too difficult. Freebase has made a data-game to let people solve these connections very quickly.
so if you are excited about semantic software, and have time this week, check out
the mappings, like everything in freebase, is creative commons.