I mean technically non-profit fan films are basically illegal for most of this stuff, on the grounds that even if you're not selling it, you're hurting their profit margins. Which is frankly rubbish, and we should definitely reform copyright law to decrease the amount of this nonsense, but even so.
The language stuff is a sideshow to the main case; it's just one of a whole list of things that the copyright holders claimed were theirs and thus in breach of copyright (some sensible, like the characters, others pretty silly, they're also claiming copyright over the shape of Vulcan ears). But it's an unusual one in legal terms, because it's basically never been legally tested whether someone can in fact own a language. If they rule that the holders can in fact own Klingon, that means hypothetically that any speech or writing in Klingon breaches their copyright, and there's enough of that now that it's a big legal area potentially.
