jLemmaGen by Michal Hlaváč.
From the webpage:
JLemmaGen is java implmentation of LemmaGen project. It’s open source lemmatizer with 15 prebuilded european lexicons. Of course you can build your own lexicon.
LemmaGen project aims at providing standardized open source multilingual platform for lemmatisation.
Project contains 2 libraries:
- lemmagen.jar – implementation of lemmatizer and API for building own lemmatizers
- lemmagen-lang.jar – prebuilded lemmatizers from Multext Eastern dictionaries
Whether you want to expand your market or just to avoid officious U.S. officials for the next decade or so, multilingual resources are the key to making that happen.
Enjoy!