The client app is not required for the extension to function, but it improves its success rate. The about section of this listing has had an entire section about the client app for years, and the privacy policy makes it clear that the extension uses third party speech recognition services to transcribe the audio file.

You should take some time to understand the technical requirements for the tools you're using, or at least read the about section twice before you start accusing people that shared their work with you.