Some more info from the Rallye-Magazin print version:

-Dr. Frank-Steffen Walliser (head of Porsche-Motorsport) is a huge rally fan, has always looked with favor upon the success of Porsche cars in Spain, Germany etc.
-Walliser has officially delegated Mr. Hermann-Josef Steinmetz (project manager for Porsche race cars) to find a base model for a rally car
-The car is based on the Porsche Cayman GT4 Clubsport (385 hp), the roll cage had to be changed, the suspension and trailing arms are reinforced and a sump guard was installed (that's pretty much everything which was changed)
-There will only be an asphalt version of the car
-They will most likely use the gearbox from the production car (six-gear PDK transmission)
-The weight is 1420 kg, that's due to the FIA-requirements (power-to-weight ratio has to be at least 3,4 kg / hp), they didn't want to reduce the number of horsepowers
-There were talks with the FIA to reduce the power-to-weight ratio to make the car more competitive, but until now the FIA wasn't willing to change anything
-They expect to be able to beat R5 cars under ideal conditions

So despite the car is entered by Dumasīteam it seems to be an official Porsche project. At least the Cayman was built in Weissach and has the official blessing of Porsche.