The EFAS data has now been made available through the Copernicus Climate Data store to all users. There are two datasets on CDS; the EFAS forecasts, and EFAS historical simulations. The latter are simulations forced with observed precipitation and temperature over almost 30 years, from 1991-2018. The EFAS forecasts are the operational forecasts with a delay of 30 days. The data is available to use under a Copernicus data license.
The publication of EFAS data in CDS was a collaboration between the two Copernicus services C3S and CEMS-Floods. Links to the data can be found on the Data Download page. Note that the documentation of the data is kept on the CDS as well as on the EFAS wiki pages.