This shall be the place to find both usage documentation and in depth tech background for our open source DataMatrix ( 2d barcode) decoder.
It is a .net (C#) component, ready to use to decode DataMatrix from bitmaps, for example shot with a cheap webcam. It's licenced as open source under the GNU General Public Licence.
libdatamatrix is an embeddable and highly extensible library made to separate datamatrix (ISO/IEC16022) functionality from image reading/writing since I needed to make a custom image scanner and couldn't find any libraries that did error correction (instead of just error checking) and had a modular interface allowing one to extend functionality easily.
libdmtx is a shared library for Linux that can be used to read (scan & decode) and write (encode & print) 2D Data Matrix barcode symbols. It is released under the LGPL and can be used and distributed freely under these terms.