Morfeusz is a morphological analyser (not stemmer, not tagger) for Polish, withouth a guesser - so it's a morphological dictionary of a kind. Note it's a library, not a ready program. There exist modules developed by external authors, allowing to use Morfeusz in Java and Python.
Implementation of Świdziński's formal grammar of Polish. Requires a parser (Birnam parser available as a separate tool) and a morphological analyser (no free analyser for Polish; Morfeusz can be used with restrictions - in this case the whole set is available for academic and non-commercial use only).