After registering please use the following acknowledgment when using CHFP/SHFP data:

"We acknowledge the WCRP/CLIVAR Working Group on Seasonal to Interannual Prediction (WGSIP) for establishing the Climate-system Historical Forecast Project (CHFP, see Kirtman and Pirani 2009) and the Centro de Investigaciones del Mar y la Atmosfera (CIMA) for providing the model output http://chfps.cima.fcen.uba.ar/. We also thank the data providers for making the model output available through CHFP."

Some data providers have additional terms and conditions for use of their data:
ECWMF restrict use to non-commercial research and require no onward distribution of data (see LICENCE from ECMWF).