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 Dumas´team it seems to be an official Porsche project. At least the Cayman was built in Weissach and has the official blessing of Porsche.