"LandDyn" are a series of GRASS-6 addon scripts created and maintained by the Mediterranean Landscape Dynamics Project (MedLanD Project) of Arizona State University. These scripts model human landuse (subsistence agriculture and/or pastoralism) and basic landscape processes such as Landscape Evolution (erosion/deposition over time), Vegetation Succession, Soil Depths, and more. There are also many scripts that calculate various variables that go into the core scripts.
LandDyn scripts may be accessed from the GRASS Addons repository: http://svn.osgeo.org/grass/grass-addons/raster/LandDyn/
Additionally, there are some scripts that are specifically made to interface with the MedLanD project's Agent Based model, AP-Sim. These scripts are in a separate subdirectory of the LanDyn Addons Repository: http://svn.osgeo.org/grass/grass-addons/grass6/raster/LandDyn/devs_landcover_scripts/.
Any questions about LandDyn scripts, or anything pertaining to the MedLanD project should be directed to Isaac Ullah: firstname.lastname@example.org