This looks pretty good. Though many of the features are already baked into PostgreSQL's full-text search, out of the box this seems to add enough value to get me interested. I'll definitely be checking this out further.
Can you clarify... does this addon simply store the Wordnet data inside Postgres, or actually let the postgres full-text search do query-expansion-to-synonyms?
[1] - https://github.com/taotetek/wordnet-postgres