There is, to put it lightly, considerable legal argument over who owns a created language or lettering system. This is an extremely interesting question.
I have written elsewhere about my love/hate relationship with Christopher Tolkien, for reasons just such as this -- he has a very, very anachronistic sense of the world. When it comes to editing something like the Legend of Sigurd and Gudrun, it comes in handy. But applied to the mutation of his father's work into a multimillion dollar media empire, his perspective is disastrous and tone deaf.
Tengwar isn't a font, it's a writing system. It's a bit like saying that Sanskrit or Katakana is a font.
In this particular case, the Tolkien estate is asserting copyright over these specific fonts made for Tengwar, but doing so as part of a larger belief that they also own the whole writing system.
When an institution declares "ownership" of a specific part of culture and wishes to control it, problems inevitably arise.