Sure, I am not a fan, but I don’t see any huge issue with this. Unfortunately, quite a lot of projects do stuff like this. If you are really concerned you can use matrix without using anything from matrix foundation (aside from the protocol) there are alternative clients like cinny. And even alternative servers like conduwuit.

Not sure if it is illegal in Germany, but laws usually aren’t so specific. Where I live we basically made “From river to the sea” illegal, because “it promotes genocide”.