The wafocitation.m program explains how to cite WAFO, and here is the text:
% To cite WAFO in publications use:
%
% Brodtkorb, P.A., Johannesson, P., Lindgren, G., Rychlik, I., Rydén, J. and Sjö, E. (2000).
% "WAFO - a Matlab toolbox for analysis of random waves and loads".
% Proceedings of the 10th International Offshore and Polar Engineering conference, Seattle,
% Vol III, pp. 343-350.
%
% or
%
% WAFO-group (2000).
% "WAFO - A Matlab Toolbox for Analysis of Random Waves and Loads - A Tutorial"
% Math. Stat., Center for Math. Sci., Lund Univ.,
% Lund, Sweden. ISBN XXXX, URL
http://www.maths.lth.se/matstat/wafo.
%
% A BibTeX entry for LaTeX users is
%
% @InProceedings{BrodtkorbEtal2000Wafo,
% author = {Brodtkorb, {P.A.} and Johannesson, P. and Lindgren,
% G. and Rychlik, I. and Ryd{\'e}n, J. and Sj{\"o}, E.},
% title = {{WAFO} - a {M}atlab Toolbox for the Analysis of
% Random Waves and Loads},
% booktitle = {Proc. 10'th Int. Offshore and Polar Eng. Conf., ISOPE, Seattle, USA},
% pages = {343--350},
% year = {2000},
% volume = {3},
% }
% @Manual{WAFO-group2000Wafo,
% author = {WAFO-group},
% title = {{WAFO} - A Matlab Toolbox for Analysis of Random Waves and Loads - A Tutorial},
% year = {2000},
% organization = {Math. Stat., Center for Math. Sci., Lund Univ.}
% address = {Lund, Sweden}},
% note = {{ISBN} XXXX},
% url = {
http://www.maths.lth.se/matstat/wafo}
% }
%
% We have invested a lot of time and effort in creating WAFO, please cite it
% when using it for data analysis.