OpenCCG, the OpenNLP CCG Library, is an open source natural language processing library written in Java, which provides parsing and realization services based on Mark Steedman's Combinatory Categorial Grammar (CCG) formalism.
The library makes use of multi-modal extensions to CCG developed by Jason Baldridge as part of the Grok system (the precursor to OpenCCG). These extensions are described in Jason's dissertation and in a joint EACL-03 paper with Geert-Jan Kruijff.
Current development efforts, led by Michael White, are focused on making the realizer practical to use in dialogue systems. See the papers on Mike's web page for details.
Also, Jason Baldridge and students at UT Austin have developed DotCCG, a new format for specifying OpenCCG grammars, and VisCCG, an editor and visualizer for grammars written in DotCCG format. These developments are described in Baldridge, Chatterjee, Palmer and Wing (2007). See the UT Austin computational linguistics lab's OpenCCG wiki, which has a number of tutorials and example grammars for DotCCG and VisCCG.
OpenCCG has been and is being used for a number of dialog systems: see the list of projects using OpenCCG. Please get in touch with Jason if you would like add yours.
For the latest news about OpenCCG, check out the SourceForge project page.