The DSSP program was designed by Wolfgang Kabsch and Chris Sander to standardize secondary structure assignment. DSSP is a database of secondary structure assignments (and much more) for all protein entries in the Protein Data Bank (PDB). DSSP is also the program that calculates DSSP entries from PDB entries.
DSSP is distributed on a basis of trust. If you want to use DSSP at MSI download the license agreement at http://swift.cmbi.ru.nl/gv/dssp/HTML/license.html Fill it out and return it to the Centre for Molecular and Biomolecular Informatics. Contact information is on the license agreement.
Additional documentation can be found at http://swift.cmbi.ru.nl/gv/dssp/