NULEXNULEX is an open-license lexicon, combining WordNet, VerbNet, and Wiktionary, linked to the OpenCyc ontology. It can be downloaded from here. If you use NULEX or create derivative works from it, we ask that you cite the following paper:
McFate, Clifton, and Forbus, Kenneth. 2011. NULEX: An Open-License Broad Coverage Lexicon. In Proceedings of the 49th Annual Meeting of the Association for Computational Linguistics: Human Language Technologies. Portland, OR.