The article is a little bit light on the details. While I don't agree with the situation, the decision is based on the law for the DWD[1]. According to §4 (1) Nr. 3 DWDG, the only public information is for weather warnings. While in reality, most other information is free, providing it for free is not the tax-payed task of the DWD. According to §4 (1) DWDG, it may only provide free information for the public if it's due to their legal obligation.

[1]: https://www.bundesgerichtshof.de/SharedDocs/Pressemitteilung...