For anyone's future reference, the university professors I spoke with recommended the following for academic or research purposes.: 1) If the survey is publicl

For anyone's future reference, the university professors I spoke with recommended the following for academic or research purposes.: 1) If the survey is publicly available and does not have controlled usage you can simply cite the source of the survey. 2) If you modify some part of it you will need to be explicit about that e.g. "as modified in October 2010 by (your name)" or "as modified by the author." For commercial purposes this might be different, in which case you should contact the publisher and make a request. My situation is for research purposes but I will contact the publisher to be sure.