I wouldn't call NaturalMotion an "Engine-maker" or Euphoria an "Engine." (That makes it sound like they're doing the same thing iD or Epic is, and they're not; their product is very different and much narrower in scope.) They don't like being called "middleware" but something more along those lines like a generic-but-accurate "Technology company" might be more appropriate?

TLDR: Unqualified use of the term "Engine" implies Euphoria is a full-scale game engine, which it isn't.