Ultimate YouTube HD Client (the application) is not affiliated with YouTube in any way. It serves as a client for YouTube, allowing users to browse and play vidoes from YouTube. The download function is intended to be used to download only the videos you own and/or for which you have rights. If you do not own the copyright of a video, you can not download it. You must obtain permission from the author to download a video, the author being the person that owns the copyright of the video.
The application does not collect and store personal identity information. It uses Microsoft Application Insights to collect telemetry of the application.