This seems like it would follow along the same lines as emulators and torrent downloaders. If you don't download anything illegal with it, you're not doing anything wrong. I use this software for work to download good resolution/low filesize copies of my client's videos. Hopefully I can continue using it.
I don't even think you need to go as far as comparing it to emulators and torrent downloaders. It just downloads what's publicly hosted on the web, it's no different from a web browser basically.